Part-American, part-Scandinavian death-metal band Dethklok has a lingering effect on its fans, who take the words seriously and do anything Dethklok lyrics say. The government fears the band's influence and sets out to destroy it by covert means; for example, by sending military pharmaceutical psychotropic drug manufacturers. Deemed sociopaths for tossing hot coffee at their concert attendees, two of the band members are alcoholics, and they all have self-esteem issues.
Despite his bandmates' warnings, Nathan begins seriously dating one of his fans. But as the evidence of her past piles up, to prove her innocence, he follows her to the most brutal place on earth: Klokikon - the annual Dethklok fan convention filled with cosplay geeks and homosexual fan art. Meanwhile, the rest of the band starts smoking after Murderface lands the cover of Smokaroonie Aficionado.
After Dethklok is accused of being racist at a huge press conference, they combat the charges by opening an Urban Youth Dethcenter. Meanwhile, Toki, after being left behind, starts a special club that promotes equality and love but excludes Murderface because he doesn't have the right look.
With their new album finally shipping, Dethklok plans their post-release traditions of vacationing, goofing off, palling around, and prank calls. Nathan, however, can't shake the feeling that something is wrong with the record... After being humiliated by Murderface's prank calls, Skwisgaar and Toki swear revenge.
Dethklok heads to Tomahawk, Wisconsin to open a Dethfair in hopes that it will stimulate the economy they destroyed. Pickles uses this time at home to reconnect with his disapproving mother who tells him that she won't respect him until he gets a real job. Pickles decides to hang up his drumsticks and goes into an even more brutal profession: he becomes a realtor.
Tired of taking verbal abuse from his bandmate, Toki writes a tell-all book called Skwisgaar Is Ams Dick and takes over as Dethklok's lead guitarist. But can Toki handle the spotlight? Meanwhile, Nathan buys a new favorite toy for the band: a defibrillator.
After spending all their time with sluts and squandering the budget on their new record, Dethklok is shocked to find they've been assigned a new producer: A WOMAN. She sends them on a pre-writing vacation that turns out to be a brutal trip to a third world country where they're mistaken as women and captured as sex slaves.
In an effort to make friends, Toki goes to Rockaroonie Fantasy Camp - a weekend getaway to rub elbows with rock and roll royalty (but he attends as a camper.) Instead of meeting friends, he is bullied by other campers and has no one to turn to but celebrity counselor, Magnus Hammersmith; ex-Dethklok guitarist with a troubled past. With Toki - the diabetic scaredy cat - out of Mordhaus, Skwisgaar and Murderface act out and over do it with candy and scary movies.
After Murderface is announced as the recipient of this year's Most Brutal Looking Musician Award, he travels to Mexico to get the best and cheapest plastic surgery possible. Meanwhile, the rest of Dethklok deal with the brutality of aging and letting themselves go.
Dethklok returns to the water to record in their new Dethsub but, plagued with the lack of women, carpel tunnel sets in from excessive masturbation. The band regresses to an animal mindset. Pickles and Nathan spend their energy crossing the workplace relationship line and competing for the only woman on the sub: their producer.
As Dethklok hosts the most important dinner of their career, the divvying of album credits, over tagging on social networking sites, and fights over a girl come to head. Can CFO keep their issues in check? Will the record executives forgive them for the past year of mistakes? Or will it be a total, brutal disaster?
While the world awaits the final Dethklok performance, members of the band prepare for their post-Dethklok careers. Pickles starts a winery for the most alcoholic wine ever, Nathan and Skwisgaar look for a brand new sound that does not suck, and Toki works with Murderface on his campaign for congressman. Meanwhile, Selatcia takes Dethklok’s weakness as the opportune time to strike!
Dethklok is notified of a looming secret that has been around for hundreds of years: the secret of the Metalocalypse. Before they can contemplate what this means, however, Nathan must give a eulogy and do the most brutal thing he has ever done: get in touch with his emotions.
