+4 252+ Def Magnezone Body Press vs. 96 HP / 60 Def Melmetal: 368-434 (84.5 - 99.7%) -- guaranteed 2HKO
160+ Atk Melmetal Earthquake vs. +2 80 HP / 252+ Def Magnezone: 160-192 (53.1 - 63.7%) -- guaranteed 2HKO
160+ Atk Melmetal Earthquake vs. +4 80 HP / 252+ Def Magnezone: 108-128 (35.8 - 42.5%) -- guaranteed 3HKO
160+ Atk Melmetal Earthquake vs. +6 80 HP / 252+ Def Magnezone: 84-100 (27.9 - 33.2%) -- guaranteed 4HKO (not needed because zone is confidend to ohko at +4, but even if it tries the total amount of damage is a minimum of 116.8% which is more than 100% + 2 rounds of leftovers)
0 SpA Heatran Magma Storm vs. 96 HP / 80 SpD Melmetal: 342-404 (78.6 - 92.8%) -- guaranteed 2HKO after Stealth Rock and trapping damage
160+ Atk Melmetal Earthquake vs. 252 HP / 0 Def Heatran: 460-544 (119.1 - 140.9%) -- guaranteed OHKO
bonus calc:
+2 252+ Atk Weavile Knock Off (97.5 BP) vs. 96 HP / 60 Def Melmetal: 229-271 (52.6 - 62.2%) -- guaranteed 2HKO
always lives knock into knock from jolly and has decent chances to do so against adamant (remember, knock loses power after it knocks the item off). if melly already used the berry, then it just comfortably takes two after rocks even from adamant.