In a metal band alot of the times the bass player uses some form of distortion, I've played bass for a long time and my favorite bass distortion is the BigMuff i use the guitar one, mine is realy old, it was my dads from 1965, but they do have a bass one. Also a chorus pedal, alot of famous metal bassists used chorus pedals like Cliff Burton in his solo along with a BigMuff and a CryBaby...