The girls will either dress similarly, or can be seen looking dangerous and sexy.
Those who favour Black Metal over other genres of metal will usually wear more black, a vast array of metal spikes, and sometimes Corpsepaint.
Either way long hair is must, for headbanging etc.
The most important aspect to being a metaller however, is a genuine love for the music, a passion which starts deep in the soul, makes your skin tingle, and has you screaming "HELL YEAH!!" If you don't get this feeling early on, the you're not ever likely to get it.
Some of the genres they will listen too include; Death, Black, Power, Classic, Doom, NWOBHM, Progressive, Thrash, Speed, Industrial, Melodic Death, Folk.
Being a metaller also often includes a lifestyle of drinking, sex, smoking, going to gigs, getting down and dirty in the Pit, and just generally immersing ones self in dedication to music, wether it be listening to or playing it, and all the knowlege which goes with it.
Metallers can spot a poser (or 'New Breed')a mile off. A true metaller is in it for life; its not a choice, its a calling.
2nd metaller; to me, its a continuation of what that music is doing, theyre pushing it to new extreme levels.
1st metaller; awesome, now lets go get some fuckin beer.