As a fan of metal music, I've noticed some traits peculiar to the genre and its fans.
First off, though I like metal music, I can rarely stand most other metal fans, taken as a distinct species.
Metal has the unfortunate feature that more than any other music genre, it splits into tiny and mutually hostile sub-genres. I didn't even know that death metal and doom metal are apparently two "very different things" until some guy tried to assault me in a mosh pit for being ignorant about this evidently crucial set of differences.
Metal concerts always have mosh pits. They are unique in that they are perhaps the only place in the world that a 6 foot, 200 pound guy in Celtic warpaint will tackle you, but will also pat you on the back and apologize profusely for knocking you over.
Also, in a mosh pit, everyone is fair game. I've seen 100 pound people get tackled and do the tackling.
Metal concerts always have women, but it can be hard to tell.
Hygiene seems to be minimal for metal fans who are really into it. I can't tell if this is more their personality or the fact that they are often teenage boys who are probably not well liked in high school.
The music is also loud.
By itself, that's not unusual among genres. But to quote psychologist Jeffrey Arnett (from Wikipedia), metal concerts are meant to be "the sensory equivalent of war." The point is to have an "onslaught of sound", and believe me, onslaught is the perfect word to describe it.
Good luck hearing anything after a concert. You'll also get neck pain from all the head banging.
I guess metal music is the genre for people who think way too much about old wars or who wish their mom would understand their inner pain. But hey, it's pretty metal.