No one who goes to a movie called “Deathgasm” is likely to expect a cerebral experience—except perhaps that heads might roll in the course of the action. And they do in this gorefest from New Zealand, which also mixes in heavy metal music and juvenile humor in a brew that aims for a campy, midnight movie vibe it never quite achieves.

The plot centers on Goth teen Brodie (Milo Cawthorne), who’s shipped off to his aunt and uncle (Jodie Rimmer and Colin Moy) after his mother goes bonkers. They’re infuriated by his devotion to what they consider satanic music, and their bullying son David (Nick Hoskins-Smith) is equally angered when Brodie attracts the eye of his girlfriend Medina (Kimberley Crossman).

Amid all his problems Brodie has the good fortune to stumble into a sort of friendship with Zakk (James Blake), an ultra-hip guy who shares his musical tastes and even agrees to join his band—which also includes nerds Dion (Sam Berkley) and Giles (Daniel Cresswell). When Brodie and Zakk break into a derelict house, they find Rikki Daggers (Stephen Ure), once the lead singer of a metal group but now a crazed wreck. It turns out he’s hiding out from Vadim (Tim Foley), the leader of a devil-worshipping cult who’s intent on retrieving a “Dark Hymn” that Daggers stole. Rikki will soon be killed by one of Vadim’s lackeys, but not before he’s sent Brodie and Zakk off with the pages.

The plot really kicks in when the band—now christened as Deathgasm at Zakk’s suggestion—plays the hymn. Everybody within earshot, except the guys and Medina, turns into a demonic monster, ravenous and bloodthirsty. Brodie and his pals band together to fight the menace, even as Vadim shows up along with his new second-in-command (Delaney Tabron) to reclaim the hymn. Much comic mayhem ensues.

“Deathgasm” assembles the basic ingredients for a goofy good time, but the makers don’t have the skill to blend them to best effect. Jason Lei Howden’s writing is limp, with only an occasional sharp line to generate a chuckle (mostly in the form of an extraneous aside), and his direction shows no real style—a complaint that can be made about Jane Bucknell’s production design and Simon Raby’s camerawork as well. Some animated graphics are employed toward the start, but that’s quickly abandoned.

As for the performances, Cawthorne can’t muster the degree of energy (or audience empathy) that he managed in the recent thriller “Blood Punch,” and Blake overdoes the rebel-without-a-brain attitude. Everyone else is fundamentally amateurish, though Crossman makes an engaging romantic interest.

“Deathgasm” is the sort of picture that would fit nicely into the schedule of the SyFy Network or its sister, Chiller. But it’s not hard to imagine how the material could have been shaped into something far cleverer.