Heatran

With access to fantastic utility moves such as Stealth Rock, Magma Storm, Taunt, and Toxic, Heatran is one of the best progress-makers in the metagame. The aforementioned movepool makes it almost impossible to stave off in the long run and allows Heatran to invariably make some kind of foothold for its team whenever it hits the field. Heatran's Fire / Steel dual typing also bestows it with a bevy of key resistances, which is paired with its fantastic natural bulk so it can check some of the strongest offensive threats in the metagame, most notably Tapu Lele, as Heatran resists both Psychic and Fairy. Two incredible abilities in Flash Fire and Flame Body help it check even more of the metagame, with the former stonewalling Volcarona, while the latter allows it to be an annoying stopgap to Weavile as well as punish multi-hit contact moves, such as Double Iron Bash from Melmetal. Despite its lack of reliable recovery and mediocre Speed tier, the guardian of volcanoes is a metagame-defining presence by burning bright in both defense and offense.