Sadly enough, metalheads, in my experiences, are at least ten times more likely to play an instrument or compose music than fans of other music. Real fans of classical and jazz music might get close. Participation in a scene might not be as twenty years ago but you'd be hard pressed to find another fanbase that has more people that have picked up a guitar/bass/drums at one point. How many listeners of rap music have tried to mess around on a sequencer before? Metal seems to inspire a desire to try to contribute that other genres do not.