Any kid who listens to, pretty much, the best music evar.
None of this metalcore (Bullet for my Valentine), hard rock (Nickelback crap), ACTUAL METAL.
If more than 2 of these are applicable to your music tastes: Shadows Fall, Children of Bodom, Arch Enemy, Lamb of God, Amon Amarth, Axenstar,
The Duskfall, Ensiferum,
Imperanon, Into Eternity, Job for a Cowboy, Cellador, Cannibal Corpse,
Naildown, Seven Kingdoms,
Warmen, Stratovarius, Wintersun, Nocturnal Rites, Waking the Cadaver
then you are probably a metal kid, and therefore cool.
Not concerned with what's in style, or "cool."
Wear band tshirts and jeans, because that's all that's necessary.
Long hair, though, is almost always a complete compliment and awesome.