Housed in a faux Marshall amp head that goes up to 11 (a cheeky nod to Spinal Tap), this four-disc Rhino box set presents a wildly eclectic look at heavy metal in its various permutations, ranging from glammed-up hard rock to fierce, pummeling thrash. Beginning with late-1960s proto-metal act Iron Butterfly (the organ-tinged "In-A-Gadda-Da-Vida") and closing with a '90s track by the revered Brazilian ensemble Sepultura (the rumbling "Dead Embryonic Cells"), the collection covers a lot of ground, making time for the opera-like drama of power metal (see Iron Maiden's "The Number of the Beast" and Helloween's "A Little Time") and the lusty rock of the leather-loving variety ( Spinal Tap's gleefully lewd "Big Bottom" and Poison's "Talk Dirty to Me"). While some may balk at having Great White and Slayer on the same disc, the strength of the compilation is in its diversity, which proves that metal is far from an easily definable genre.