With a musical movement like metal, being significant, staying relevant, and still having room to experiment while perfecting your craft is always a difficult combination of skills to possess. The genre calls for solid commitment to unyielding volume, viciously downtuned notes and hellish distortion, with vocals that span from the powerful to the deranged, and lyrics that cross a general spectrum of darkness, mayhem, and more-than-mild discontent. To introduce any additional elements into this equation makes a solution extremely difficult to arrive at, but for the Atlanta metal masterminds of Mastodon, experimentation is simply the bolt of lightning that breathes life into their compositions, which have not at all dwindled in their ferocity from album to album.