I've never been a metalhead, but I skirted around it for a bit in my younger, angrier days, and many of friends were pretty 'metal.'
I was always a bit mainstream though; Metallica, Pantera, Sepultura, Fear Factory (I still listen Demanufacture on occasion), then later onto System of a Down and Slipknot. I was more into 'hard rock / sorta metal' though; RATM, Tool, Rob Zombie, At The Drive In, ...Trail of Dead, that sort of thing.
I have been to plenty of metal gigs, and I will say this; despite how they look, Metalheads are generally some of the nicest and well-behaved people you'll ever spend time at a concert with.
And the moshpits are insane, if /when you're into that sorta thing. The 'jump the f*ck up' part in Slipknot's Spit it Out is the biggest beating I've ever copped in my life.