Depends: the best live band I've seen is SLAYER, by far. However, the best metal band, that's tough. I would likely say Pantera, but I'm a Phil Anselmo junkie (not literally). It also kinda depends on what you're looking for, for example, if you don't want to get beat up real bad, don't go to a slayer show, and try to get up front (always do anyways
). Much as I hate to say it, because they sold out, old school Metallica is still pretty sweet.