drums are needed. they keep the beat and can have some of the best parts of a song. the bass and guitar are equal. for diffrent reasons.
bass keeps rhythm and can keep a melody. cause really when a guitar solo is going you cant headbang to it, they dont have much rhythm. you're headbanging to the bass, drums and maybe rhythm guitar and enjoying the solo.
guitar can keep a better melody and can do crazier stuff, but usually sounds like crap without a bass. ever hear the white stripes live? it's hollow. there's drumms and Jack going nutzo on his guitar with no low end to back him up (for songs like 7 nation army anyway)
so yeah.
