Heatran

Steel

Heatran is one of the most important Pokemon for Steel teams because of Flash Fire, which gives it a unique immunity to Fire, meaning every team is required to use it. It also has a unique role in using Magma Storm to trap and remove many walls that Steel may otherwise struggle to get past, such as Mega Venusaur, Toxapex, and Slowbro. Heatran's offensive and defensive base stats are mostly respectable, allowing it to have great power and bulk even without investment in those stats. As a result, it has great versatility, being able to use both offensive and defensive sets that can provide a wide range of different utility with its amazing movepool that includes Stealth Rock, Taunt, and Toxic. Unfortunately, Heatran's Fire typing is terrible defensively, exacerbating its weakness to Ground, bringing with it an annoying weakness to Water as well, and failing to even be useful because Flash Fire provides an immunity to Fire anyway. Its Speed is also quite poor, as it's forced to run a Timid nature for a usable Speed stat and still gets outsped by even neutral-natured base 90s like Meloetta. Uninvested Heatran is even outsped by Mega Venusaur, which it is supposed to check. Worst of all, Heatran lacks proper recovery, leaving it very vulnerable to being worn down and taken out over time.

Fire

Heatran compresses many useful roles for Fire teams due to its all-around good stats and unique typing. Exclusive access to Magma Storm combined with Taunt lets Heatran trap and break walls like Chansey found on balanced teams that otherwise can be major obstructions for its teammates. Heatran's Steel typing grants it a key neutrality to Rock-type moves, letting it check massive threats to Fire teams like Mega Diancie and Choice Scarf Nihilego. Heatran's wide movepool can also let it fill other roles for a team, such as providing Stealth Rock or spreading status, though it faces competition from Torkoal in these areas. However, Heatran's 4x weakness to Ground forces it to use Air Balloon to check Earth Power Mega Diancie and leaves it forced out by defensive Ground-types like Swampert and Gliscor after its Air Balloon is popped, preventing it from effectively stallbreaking teams while these Pokemon are healthy enough to switch into it. Heatran also has a very mediocre Speed stat and is slower than some faster walls like Zapdos and Gliscor even with maximum Speed investment.