It is matched in its renewed vigor by a growing crop of classic metal bands that have staggered out of the '90s with new tours, new albums, reunited lineups, and a new generation of fans, including their Bay Area peers Testament, Exodus, and Death Angel.

These graying warriors have been introduced to younger audiences by a proliferation of national package tours, which bundle large stables of artists to appeal to the widest possible audiences, leading in turn to widespread temporal and subgeneric cross-pollination. The venerable Ozzfest franchise led the charge before succumbing to economic privation, though not before a 2005 spat between the members of Iron Maiden and Ozzy Osbourne's wife-cum-manager Sharon culminated in the indefatigable Irons being hassled onstage by her egg-throwing minions.

The release of Guitar Hero II (Harmonix/RedOctane/Activision) in 2006 was similarly instrumental in the revitalization of metal and guitar-driven music more generally. Though the first installment sold well, it was the sequel that ushered in the phenomenon as we know it today, and an unimpeachable track list opened the ears of the video-gaming public to a world of distorted possibility. It was as adept at resurrecting older artists as it was at breaking younger ones, and metal mainstays like Mastodon and the Sword owe the tastemakers at Harmonix a debt of thanks.

Mastodon's rise to prominence as America's premier young metal band marks a fitting end to this decade of destruction. Raised on '70s prog, '80s thrash, and the hardscrabble underground music of the '90s, its music is as aggressively technical and high-brow as Limp Bizkit's was simple and mookish. 2003's Leviathan (Relapse) and follow-ups Blood Mountain (Relapse, 2006) and Crack the Skye (Relapse, 2009) encapsulate an era hungry for music that is simultaneously heavy, challenging, and as ambitious as the output of metal's resurrected masters. Now we must await the riffs of this century's teenage years.