Golem is one Pokemon (along with Rhydon) that should be considered on nearly every team. Its role as a resistance to Normal-type moves and immunity to Electric-type moves cannot be understated. These defensive capabilities cannot be duplicated by any other type of Pokemon, and effectively stops several Pokemon from running rampant through the metagame. It completely walls Electric-types (with the exception of Surf Raichu) that would normally be game-breaking, he takes Normal-type attacks and shrugs them off as if they were nothing, and then he hits back with a powerful STAB Earthquake.
Whether to use Golem or Rhydon has been an age old question for all RBY players. They each have their advantages over the other, and the decision is completely up to the trainer. Golem is slightly faster and packs Explosion, while Rhydon has a higher Attack and can take hits slightly better due to its higher HP, although the difference is minuscule. Either choice is a solid option and should be considered when building a team.
Golem is an extremely valuable Pokemon that should be considered on every team due to its amazing Defense, very good Attack, and important resistance to Normal-type attacks. Earthquake and Body Slam are its main attacks, with Rock Slide and Explosion playing specialty roles. Earthquake is a really solid attack that does plenty of damage to anything not immune or resistant to it. Body Slam is the backup, used for predicting switches and inflicting paralysis, something Golem appreciates quite a bit. Rock Slide is for any Flying Pokemon that Golem comes across and the odd Lapras or Jynx.
Explosion is the last ditch effort to remove any problematic Pokemon or to do massive damage before Golem is KOed by the opponent. The threat of an incoming Explosion will always be on your opponent's mind, and it is important to not use Explosion at an overly obvious time to avoid Exploding right into a Gengar or opposing Rock-type. The threat of Explosion is a great tool for playing prediction games with your opponent, as if you play it right, you can Earthquake a Gengar coming in to nullify your Explosion.
Golem does not have the movepool for any additional options, although Substitute can be used over Rock Slide if you deem Rock Slide to be ineffective.
Checks and Counters
Exeggutor is probably Golem's best counter, as it takes very little damage because of its decent defenses, resistance to Earthquake, and ability to hit back with a 4x super effective Mega Drain or a powerful STAB Psychic. Venusaur and Victreebel can come in on Golem and threaten with Razor Leaf, but will take a large chunk of damage from Earthquake. Slowbro takes very little damage because of its great Defense and can OHKO with Surf. Starmie can counter it, but will take a powerful Earthquake on the switch in for about 45%.