It’s bedlam backstage at Hartwall Arena in Helsinki, Finland. Mastodon and Lamb of God have both finished their sets and are done for the evening. Metallica, the night’s headliners, just hit the stage, and the crowd’s going expectedly ape. Yet while there is, undeniably, a party going on in the venue proper, as Hetfield and Hammett lay down their majestic Death Magnetic riffs, there’s also a chaotic bash backstage, where the opening bands and their crews have run of the place. That can only mean one thing: trouble.

“Man, I so don’t want to be doing this interview right now,” admits Brent Hinds, clearly preoccupied and a little stressed, like a teen that wants to get to the party but his Mom won’t cough up the car keys. “I’ve been waitin’ all damn day to party with these guys, my bros Mark (Morton) and Willie (Adler) in Lamb of God. No offense, dude, but I mean, we’re in Finland! What the hell else are we supposed to do? Hold on a sec…”

Hinds puts down his cell phone and the background noise rises up. There are whoops and hollers, the kind you’d hear at a rodeo, including Hinds’ own. His interview had obviously come at a bad time, but then Hinds manages to uh, multitask. A good two minutes passes before he returns to the phone, apologizing, “Sorry, man, but I had to do that.” He remained vague about what that was, though his voice had slowed somewhat and he seemed more relaxed. “Mark and Willie tell me you and the mag are super cool, so let’s do this. We can do this!”

To ease the pain of his interview, I explain that we’ll be talking about guitar playing, his favorite subject, hands-down. “Dude, I can polish that turd all day long,” he says. “Right now, I feel like I can sell a Popsicle to an Eskimo. I’m livin’ the dream! Hell, I used to build houses every day, and now I’m onstage playing my guitar. My guitar is helping me build my own house.”

In Crack the Skye, Mastodon’s fourth album, the band has poured a fresh new slab foundation for that house, a monolithic ode to rock and roll, capped by a soaring spire that is as impressive to hear as it is difficult to comprehend. The song cycle, an abstract ode to astral travel, is brainy and brawny all at once, intricate, but pulverizing and electric. It is the sound of a band stretching itself to the point of snapping, a game of “chicken” that ends not in a last-ditch avoidance to safety but in an explosive, head-on collision. Says Kelliher, “We wanted to make a prog record that sounded like it was from the ’70s but is actually from the future.”

At the core of this vintage futurism stand Hinds and Kelliher, whose dueling guitars wind around each other like a pair of poisonous snakes, twisting in tightly as each track spirals higher. Hinds leads the way in unorthodox fashion; he’s a hybrid player, combining fingerpicking techniques with traditional picking, a result of his education early on as a student of classical guitar. By his side, Kelliher observes, listens, and then complements his colleague, creating his own parallel path. “Brent’s a total shredder,” Bill says. “I try to keep shit down and leave it at that.”

Mastodon’s extraordinary finished product does not go unnoticed, in the metal community and way beyond. “When we first met Metallica in Portugal,” Kelliher recalls, “Kirk Hammett and Rob Trujillo walked up to me and said, ‘Dude, it’s really nice to meet you.’ And I’m like, ‘Nice to meet me?’ Seriously, I’m face to face with the metal gods of my life and they’re happy to meet me?

He continues, “Pepper Keenan of Down (and Corrosion of Conformity) came up to me one night after our show, punched me hard in the arm, and said, ‘Man, I just saw metal evolve before my very eyes!’ All of this is pretty damned flattering.”

Back in the late ’90s, when the band formed, Mastodon had somewhat milder ambitions. They were loud and proud, of course, bludgeoners primarily, with a moody, progressive aesthetic that set them apart. Then something strangely tragic happened. After they signed with Warner Brothers in 2006, and released and toured the Grammy-nominated Blood Mountain, Hinds suffered a traumatic head injury backstage at the MTV Video Music Awards. A fringe lunatic in the Wu Tang rap posse sucker punched Hinds and the blow put him in a coma. His brain had swelled so much from the impact that authorities notified his family, in case he didn’t come out of it.