Though actually, maybe Game Freak were onto something with giving Charmander Metal Claw which they should've kept going with.
If I were to say what type is most closely related to Steel-Type and thus should get the most Steel-Type coverage, what would you say? It's Fire-Type, right? But a lot of Fire-Type Pokémon don't learn any Steel-Type moves, even though magma is kind of a mix between Fire- and Steel-Type attributes. And when you look at what type does receive a lot of Steel-Type coverage -- Ice-Type because I guess shiny -- it becomes even more confusing because Fire-Type is also luminescent. <--- I decided to double check this, and believe it or not Dragon-Type is actually the type with the most Flash Cannon coverage. Kyurem is a big reason for this, though, and discounting it and its forms, Dragon- and Ice-Type tie.
Basically, I'd argue that most Fire-Type Pokémon should almost learn Flash Cannon by default, and it's a pretty small minority that actually do (Camerupt, Volcanion, and Turtonator if you were wondering, Heatran excluded since it's not coverage for it). If Pokémon like Vanilluxe learn Flash Cannon, Pokémon like Magmortar definitely should be able to too.
The current conversations in OI have basically just made me realise that Game Freak has no idea what Steel-Type moves should be or who should be able to learn them. Perhaps Copperajah's cool Steel-Type Stealth Rock will be introduced next gen as a regular move and distributed widely (preferably with a caveat that you can only have one of Stealth Rock and the Steel-Type variant on your opponent's field at a time) to actually give Steel-Type a meaningful status move. Because right now, the best tanky Steel-Type Pokémon only use Gyro Ball for a Steel-Type move, and even then not always, which is weird for the "tanky" type.
I was thinking mainly of special Steel-Type moves because it's the more underutilised side of the type, but FTR the type with the most Iron Head coverage is actually Ground-Type, not Rock-Type like some may assume. Ground- and Steel-Type do also have a lot in common, so seeing unlikely contenders like Hippowdon, Mamoswine, and Garchomp get Iron Head despite not having a hugely apparent connection to the move is pretty cool.
Also TIL Aromatisse learns Flash Cannon for... some reason. Go figure.