Every now and then metal dudes and dudettes toss around one of the great, unanswerable questions that has vexed metal scholars for decades. No, not "Who's gonna go to the store for more beer?" but the question of which band was heavier, Black Sabbath or Led Zeppelin. Heavy metal would not exist without Black Sabbath, but Led Zeppelin also had a lot to do with how heavy music took hold in pop culture. Led Zeppelin was one of the biggest rock bands of all time. There are but a few bands I can think of that put "big" into perspective like them. However, the relatively recent acceptance of metal into pop culture has cemented Black Sabbath as one of the most important bands in the evolution of all of rock's sub genres. Black Sabbath's fans are just as fanatical now as they were forty years ago. Both bands affected the trajectory of heavy music as much as any other band I can think of, and both had a vibe that freaked the hell out of people who were not fans of their music. I'm not sure that I can really answer this question in a way that will satisfy everyone, but I can give it a shot. This is probably a volatile topic for a lot of people, so I'll try to be careful.