All these definitions are bullshit. Metalheads do NOT follow a specific look or all listen to the same bands. What's considered "metal" is so diverse and open ended that there are tons of different types of metal heads. You've got your mainstream nu-metal/metalcore, thrash, death, black, power, grind, all of that kind of stuff, and everybody enjoys different kinds of metal outside of the mainstream metalheads and perceptions of them. You don't have to exclusively listen to Slayer, Metallica, or Cannibal Corpse. Hell, you don't even have to like any of the "classic" bands. You don't need to be a long haired, dim-witted delinquent either. Or drink/do drugs. You can dress however you want; you wouldn't be able to tell some metalheads apart from people who despise metal because they look the same. As long as you like some form of the metal spectrum, it's all good.
listen to whatever you like and don't be bound to to supposed "mandatory" metalhead bands. Explore as much metal as possible.