Heya, this is my first RMT so please don't be too mean ;-; please read all the way through before commenting, as i've given a synopsis of the basic team dynamic there.
Metagross @ Occa Berry
Adamant with 252hp/236atk/20spe
Bullet Punch
Meteor Mash
Earthquake
Stealth Rock
Leading with metagross has its perks, the best being that it counters the majority of common leads with less that 60% damage on itself. In fact, against most SR users, it even comes out completely unscathed. Much of the time you'll have to switch him out on their counter, then switch him back in to SR on an easy switch. Playing defensively with this metagross is a big deal, as he is pretty bulky and can come back later to take out a pesky pokemon or two. If you can't get the KO, I would suggest just switching into a defense that can take the opponent's lead and bringing metagross back. If you think you can get up SR, like against swampert, then do that first.
This metagross is speed trained to be able to hit other lead metagross first, and if they aren't running earthquake then that's an easy win.
Azelf is hit to sash limits by meteor mash, and finished with BP while azelf's fire blast will do 38-45% if he chooses not to put up SR or taunt with his first attack.
Swampert walls metagross easily, but allows for SR turn 1, and then an extreamly easy switch in for breloom as his EQ hits less than 30%, meaning that in the two turns breloom is probably going to be out most of that will heal and leave only SR damage.
Jirachi can do very little to metagross, and is a 2hko with EQ. If jirachi tricks, just make sure you lock into EQ and force his switch/die, and use the added speed later to help take out threats.
Aerodactly takes over 50% from BP, so just BP it twice, it chooses between SR or taunt before you kill it.
Infernape is an easy 2hko with eq/bp combo, and with occa berry lead ape hits less than 60% with fire blast.
Metagross hits 45-54% on roserade leads that sleep, I would suggest allowing the sleep after BP, since if the sleep misses you have the possible 2hko, and if not its still decent residual damage. Once gross is asleep, just send out blissey and para their switch, useing gross as a wall until he wakes up.
Heatran is a dilemma. If he tries first to set up SR, its a decently easy win, taking 69% or less damage. If he just goes strait for the fire blast/earth power however, he will 2hko metagross. I would suggest taking the first hit, as it is not completely crippling but will tell you what attack heatran will be using. If its fire blast, your heatran is scarfed, and can easily earth power the other before it can attack. If it is using earth power, i would suggest gengar. Sub turn 1 and see if he's switching, if not focus blast, if he switches to a pursuit user (unless its scizor, which is an easy ko) then just switch again.
Against Tyranitar leads, meteor mash hits 83-98% while the opposing EQ results in metagross losing less that 55%. Bp out on the second turn.
Gliscor will often start with a taunt to prevent SR. Meteor mash doesn't quite hit 50% of his hp, but its a good free hit. Lead gliscor can do almost nothing to gengar, as it carrys only ever u-turn and eq, so get gar out there to take the eq and grab a free sub.
Breloom @ Toxic Orb (Poison Heal)
Jolly with 252Atk/252Spe/4def
Spore
Substitute
Seed Bomb
Focus Punch
The ol' standby breloom, a reliable counter to many slow bulky pokemon that cause metagross and the other walls on the team problems. It can easily take an EQ from a bulky lead like swampert and get a free sleep. He compliments this team well, as he can destroy opposing walls with sleep or powerful attacks from behind a sub. He is also useful because of his healing, meaning that if you switch breloom in on something with para, you can get an easy 5-6 chances to get a free sub without sleeping the first opponent. This is useful because then breloom can sleep counters to it, or be useful after it has already slept an opposing pokemon and has been forced to switch out.
After the first turn on breloom, he can also be used as a reliable status absorber, allowing him a free switch and keeping your walls healthy. Breloom is just used to wreck the stability of a team by sleeping and causing damage. After his sub is killed, just switch into a wall that can take the next hit, or gengar/heatran with an immunity.
Gengar @ Life Orb
Timid with 252Spe/252Satk/4def
Shadow Ball
Substitute
Hidden Power(Fire)
Focus Blast
Despite having life orb, sweeping is not this gengar's main purpose. Blissey draws tons of EQs and fighting type moves as well as explosions, and Gengar can easily turn these to an advantage. It can be used late game for sweeping if you don't need to use it to take a hit, so it plays whatever role you need at the time. Scizor and Tyranitar are common switches into gengar, as they take little damage from his shadow ball and can kill him with either BP or pursuit. If you take an immunity hit with gengar, it is probably a really good idea to start by using substitute. If an opponent sends out scizor, HP fire is an easy OHKO from behind the sub. If he sends out tyranitar, its a free switch out into something like breloom that can take a scarfed tar's pursuit easily, and gets a sleep off on either it or the switch.
Heatran @ Choice Scarf
Hasty with 252Satk/252Spe/4def
Fire Blast
Explosion
Earth Power
Dragon Pulse
Heatran takes fire hits, and retaliates with a full power assault. He will be switched back out after that first hit almost every time, but taking the fire damages for skarmory is important. With SR earth power kills Infernape, and takes out Tyranitar on the 2hko if it switches in on it (it does 58-68%, so with spikes/sr out that can turn to a ohko if you've scouted it with gengar already once and its switching back in). These are both important kills for this team, as scarfed tar can cause problems for gengar and infernape can break the two walls.
Heatran really doesn't have a weakness when played this way, as he doesn't normally take damage except from SR/spikes or pursuit, which is rare and hits next to nothing. He can also be used to draw out EQs, which are breloom, skarmory, and gengar's best friend.
Skarmory @ Shed Shell (Keen Eye)
Impish with 252hp/64Atk/176def/16spe
Spikes
Roost
Brave Bird
Whirlwind
Skarmory is the physical wall for this team. He can take most physical hits with ease, and can whirlwind away most SD or DD users who are using a switch as setup. Spikes make kills easier for gengar and breloom, and can cause enough damage over time with the amount of switches that this team forces that opponents become weak and easy prey for a fast sweep like gengar. The set is the standard Spiker set with spikes chosen over SR because of metagross.
Skarmory has fire and electrical problems, but they can easily be fixed by blissey or heatran. If your opponent uses a special attack, switch to blissey and start throwing para everywhere. All fire type hits can go to heatran, as he absorbs them and can counter most pokemon that use fire after flash fire increases his power. Physical lightning isn't unheard of, but breloom or metagross can take the hit if skarmory can't wall it (mostly only if skarmory switched into an electric hit).
Blissey @ Leftovers (Natural Cure)
Calm with 252hp/200def/56sdef
Softboiled
Thunderwave
Aromatherapy
Flamethrower
Blissey can take pretty much any special attack that isn't buffed to +4, so she's a solid choice to wall out special attackers. Flamethrower is to predict and take out Scizor or other steel pokemon that commonly counter blissey. The EVs are set to help with defense in the case that scizor pursuits or a normally special pokemon runs a surprise physical move. They are calculated to keep common physical damages below 50%, so blissey can switch back in on a special hit and recover. Aromatherapy can prevent sleep spreading pokemon from creating a problem by sleeping skarmory or metagross and gets rid of para and poisons, which can be useful, especially to gengar and breloom (if it switches into para and doesn't get poisoned, for exapmle).
Explosions go to gengar. Fighting goes to gengar or skarmory. Other physical attacks go to skarmory, heatran or breloom if it can get a good switch in.
Summary:
The philosophy of this team is to have the switch ins hidden as long as possible, and pull them out when they can be really damaging to opponents. None of your pokemon should need to be sacrificed to hurt something as there is almost always an easy switch in for little or no damage. The combined damage from the opponent switching into attacks and SR/spikes will eventually make them fall (gengar stops spinning as well), and the paralysis can cause just the right timing for breloom to sweep a good number of weakened pokemon.
Thanks for taking the time to tell me what you think of my team. I would appreciate if you gave me useful and well developed advise and ideas.

Metagross @ Occa Berry
Adamant with 252hp/236atk/20spe
Bullet Punch
Meteor Mash
Earthquake
Stealth Rock
Leading with metagross has its perks, the best being that it counters the majority of common leads with less that 60% damage on itself. In fact, against most SR users, it even comes out completely unscathed. Much of the time you'll have to switch him out on their counter, then switch him back in to SR on an easy switch. Playing defensively with this metagross is a big deal, as he is pretty bulky and can come back later to take out a pesky pokemon or two. If you can't get the KO, I would suggest just switching into a defense that can take the opponent's lead and bringing metagross back. If you think you can get up SR, like against swampert, then do that first.
This metagross is speed trained to be able to hit other lead metagross first, and if they aren't running earthquake then that's an easy win.
Azelf is hit to sash limits by meteor mash, and finished with BP while azelf's fire blast will do 38-45% if he chooses not to put up SR or taunt with his first attack.
Swampert walls metagross easily, but allows for SR turn 1, and then an extreamly easy switch in for breloom as his EQ hits less than 30%, meaning that in the two turns breloom is probably going to be out most of that will heal and leave only SR damage.
Jirachi can do very little to metagross, and is a 2hko with EQ. If jirachi tricks, just make sure you lock into EQ and force his switch/die, and use the added speed later to help take out threats.
Aerodactly takes over 50% from BP, so just BP it twice, it chooses between SR or taunt before you kill it.
Infernape is an easy 2hko with eq/bp combo, and with occa berry lead ape hits less than 60% with fire blast.
Metagross hits 45-54% on roserade leads that sleep, I would suggest allowing the sleep after BP, since if the sleep misses you have the possible 2hko, and if not its still decent residual damage. Once gross is asleep, just send out blissey and para their switch, useing gross as a wall until he wakes up.
Heatran is a dilemma. If he tries first to set up SR, its a decently easy win, taking 69% or less damage. If he just goes strait for the fire blast/earth power however, he will 2hko metagross. I would suggest taking the first hit, as it is not completely crippling but will tell you what attack heatran will be using. If its fire blast, your heatran is scarfed, and can easily earth power the other before it can attack. If it is using earth power, i would suggest gengar. Sub turn 1 and see if he's switching, if not focus blast, if he switches to a pursuit user (unless its scizor, which is an easy ko) then just switch again.
Against Tyranitar leads, meteor mash hits 83-98% while the opposing EQ results in metagross losing less that 55%. Bp out on the second turn.
Gliscor will often start with a taunt to prevent SR. Meteor mash doesn't quite hit 50% of his hp, but its a good free hit. Lead gliscor can do almost nothing to gengar, as it carrys only ever u-turn and eq, so get gar out there to take the eq and grab a free sub.

Breloom @ Toxic Orb (Poison Heal)
Jolly with 252Atk/252Spe/4def
Spore
Substitute
Seed Bomb
Focus Punch
The ol' standby breloom, a reliable counter to many slow bulky pokemon that cause metagross and the other walls on the team problems. It can easily take an EQ from a bulky lead like swampert and get a free sleep. He compliments this team well, as he can destroy opposing walls with sleep or powerful attacks from behind a sub. He is also useful because of his healing, meaning that if you switch breloom in on something with para, you can get an easy 5-6 chances to get a free sub without sleeping the first opponent. This is useful because then breloom can sleep counters to it, or be useful after it has already slept an opposing pokemon and has been forced to switch out.
After the first turn on breloom, he can also be used as a reliable status absorber, allowing him a free switch and keeping your walls healthy. Breloom is just used to wreck the stability of a team by sleeping and causing damage. After his sub is killed, just switch into a wall that can take the next hit, or gengar/heatran with an immunity.

Gengar @ Life Orb
Timid with 252Spe/252Satk/4def
Shadow Ball
Substitute
Hidden Power(Fire)
Focus Blast
Despite having life orb, sweeping is not this gengar's main purpose. Blissey draws tons of EQs and fighting type moves as well as explosions, and Gengar can easily turn these to an advantage. It can be used late game for sweeping if you don't need to use it to take a hit, so it plays whatever role you need at the time. Scizor and Tyranitar are common switches into gengar, as they take little damage from his shadow ball and can kill him with either BP or pursuit. If you take an immunity hit with gengar, it is probably a really good idea to start by using substitute. If an opponent sends out scizor, HP fire is an easy OHKO from behind the sub. If he sends out tyranitar, its a free switch out into something like breloom that can take a scarfed tar's pursuit easily, and gets a sleep off on either it or the switch.

Heatran @ Choice Scarf
Hasty with 252Satk/252Spe/4def
Fire Blast
Explosion
Earth Power
Dragon Pulse
Heatran takes fire hits, and retaliates with a full power assault. He will be switched back out after that first hit almost every time, but taking the fire damages for skarmory is important. With SR earth power kills Infernape, and takes out Tyranitar on the 2hko if it switches in on it (it does 58-68%, so with spikes/sr out that can turn to a ohko if you've scouted it with gengar already once and its switching back in). These are both important kills for this team, as scarfed tar can cause problems for gengar and infernape can break the two walls.
Heatran really doesn't have a weakness when played this way, as he doesn't normally take damage except from SR/spikes or pursuit, which is rare and hits next to nothing. He can also be used to draw out EQs, which are breloom, skarmory, and gengar's best friend.

Skarmory @ Shed Shell (Keen Eye)
Impish with 252hp/64Atk/176def/16spe
Spikes
Roost
Brave Bird
Whirlwind
Skarmory is the physical wall for this team. He can take most physical hits with ease, and can whirlwind away most SD or DD users who are using a switch as setup. Spikes make kills easier for gengar and breloom, and can cause enough damage over time with the amount of switches that this team forces that opponents become weak and easy prey for a fast sweep like gengar. The set is the standard Spiker set with spikes chosen over SR because of metagross.
Skarmory has fire and electrical problems, but they can easily be fixed by blissey or heatran. If your opponent uses a special attack, switch to blissey and start throwing para everywhere. All fire type hits can go to heatran, as he absorbs them and can counter most pokemon that use fire after flash fire increases his power. Physical lightning isn't unheard of, but breloom or metagross can take the hit if skarmory can't wall it (mostly only if skarmory switched into an electric hit).

Blissey @ Leftovers (Natural Cure)
Calm with 252hp/200def/56sdef
Softboiled
Thunderwave
Aromatherapy
Flamethrower
Blissey can take pretty much any special attack that isn't buffed to +4, so she's a solid choice to wall out special attackers. Flamethrower is to predict and take out Scizor or other steel pokemon that commonly counter blissey. The EVs are set to help with defense in the case that scizor pursuits or a normally special pokemon runs a surprise physical move. They are calculated to keep common physical damages below 50%, so blissey can switch back in on a special hit and recover. Aromatherapy can prevent sleep spreading pokemon from creating a problem by sleeping skarmory or metagross and gets rid of para and poisons, which can be useful, especially to gengar and breloom (if it switches into para and doesn't get poisoned, for exapmle).
Explosions go to gengar. Fighting goes to gengar or skarmory. Other physical attacks go to skarmory, heatran or breloom if it can get a good switch in.
Summary:
The philosophy of this team is to have the switch ins hidden as long as possible, and pull them out when they can be really damaging to opponents. None of your pokemon should need to be sacrificed to hurt something as there is almost always an easy switch in for little or no damage. The combined damage from the opponent switching into attacks and SR/spikes will eventually make them fall (gengar stops spinning as well), and the paralysis can cause just the right timing for breloom to sweep a good number of weakened pokemon.
Thanks for taking the time to tell me what you think of my team. I would appreciate if you gave me useful and well developed advise and ideas.