Behemoths, fire ants and sea beasts, oh my! Mastodon is that rare band that transcends genres and transports listeners, assaulting and overwhelming the senses and the imagination. Ambitious, careening, unpredictable heaviness is the order of the day for this colossal destroyer from Atlanta (not Atlantis). On the eve of the release of its third full-length album, Blood Mountain, Mastodon is finally favoring Midwesterners with a much-needed metal bludgeoning that will blow minds like an iron tusk through the frontal lobe: heavy riffs, virtuoso drumming (provided by principal songwriter Brann Dallor) and earth-shaking vocals. Surprise ear candy, including the occasional country lick (“Megalodon,” off Leviathan), brings to bear a metal experience that even a 19th-century literary scholar could rock out to. Just don’t wear your monocle in the mosh pit.