Long after the death of his father, Brodie's mother is institutionalized at a mental hospital. The teenager is thus obliged to move into his uncle's place in Greypoint. Brodie is a heavy metal fan, which conflicts with Uncle Albert's orthodox Christian beliefs. His fellow high school students regard him as an outcast, which leads to bullying from other boys (including his cousin, David). Brodie's only friends are two "geeks" named Dion and Giles, both of whom spend most of their time playing role playing games. Brodie soon becomes acquainted with another heavy metal fan, Zakk, at a local record store. Shortly after, Zakk, Brodie, Dion, and Giles form a metal band called 'DEATHGASM'.
To Brodie's surprise, the beautiful Medina appears to be interested in him and invites him to have ice cream with her. However, Brodie is too shy and misses the chance to kiss Medina by the end of the date.
Later, Zakk tells Brodie about the metal musician Rikki Daggers, who is allegedly living nearby. Zakk convinces Brodie to accompany him to an abandoned house, where he suspects Daggers to be hiding. After breaking in, they find Daggers sleeping inside, holding a record album. When Brodie and Zakk try to steal the album, Daggers wakes up and attacks. When he hears a noise in his house, he hands them the record and tells them to run away. Moments after Zakk and Brodie have left, a well-dressed man enters the house and kills Daggers. He appears to be part of a cult which is looking for "The Black Hymn," medieval sheet music with the power to summon demons. Since the killer failed to obtain the sheets of music, the cult's leader later has him beheaded.
At home, Brodie notices the sheets of music hidden inside of the record's cover. The band plays the song, as lights flicker in response. Brodie's Uncle Albert, who is outside, hyperventilates and starts to bleed from his eyes. Brodie senses that something is wrong, and abruptly stops playing his guitar before they manage to complete the hymn.
The next day in school, Brodie translates the Latin writing on the old sheets of music. He finds out it reads: "The black hymn. Play it to invoke the demon.". On the way home, Brodie's cousin David lies in wait for him and beats him up violently to make him stay away from Medina, in whom he is also interested.
In the meanwhile, Medina meets Zakk by chance. She tells him that she could not find Brodie and asks him to give him a note. Zakk reads the note and finds out Medina wants to meet Brodie at the local park in the late evening. He does not pass it on to Brodie, but goes there himself and lies to Medina that Brodie does not want to see her. Then he puts his jacket around her shoulders and they kiss.
Brodie suspects that playing the Black Hymn is somehow connected to dark forces. Due to the humiliation by David and his friend, he wants to take possession of these powers to take revenge and therefore calls the band together to play the hymn.
After having played it, the stereo equipment explodes and all band members fall unconscious. After waking up, all four notice that something has changed. Brodie meets a strange and frightening being in the school's toilet, who threatens him and one of the teachers starts to bleed from his body's orifices and throws up blood on a student during a lesson.
In the evening, Brodie meets Zakk in a repair shop to tell him what happened where they are attacked by Zakk's father. The latter acts as if possessed, tears out his own eyes and then tries to kill them, but the two manage to defend themselves and kill him.
Meanwhile, Dion and Giles also are attacked and nearly killed by a possessed, but Medina manages to save them by killing it using an axe. They decide to hide in the school's panic room and leave a note on Brodie's door to inform him about their whereabouts.
Trying to find out what is happening, Zakk and Brodie meets with a fortune teller. She tells them they have invoked the demon Aeloth "The Blind One" by playing the hymn, and that the residents of town are now possessed by Aeloth's minions, which kill every human being in order to prepare Aeloth's arrival. By 3 AM, Aeloth will merge with the most evil human being present. Before she is able to tell them how to undo Aeloth's summoning, she is killed by two of the possessed.
Zakk is not interested in fighting Aeloth any further and decides to watch the town's doom from a nearby hill, but Brodie manages to convince him to help because he assumes the summoning will be undone by playing the Black Hymn backwards. They drive to Brodie's house to obtain the sheets of music. However, Zakk secretly removes the note stuck to the door by Dion, Giles and Medina and the sheets of music are blown out of the window by the wind. Suddenly, they are attacked by Brodie's uncle Albert and his wife Mary who have also been possessed, but manage to kill them using three dildos and a chain saw. In contrast to his parents, Brodie's cousin David has not transformed yet, but Brodie decapitates David anyway as he enters the room..
Having decided they will search the sheets of paper, Zakk and Brodie craft a few weapons and go after them.
In the meantime, the members of the cult have come to Greypoint to serve Aeloth. They meet the strange and frightening being which Brodie had met in the school's bathroom. It appears to be Aeloth's ambassador who promises the cult's leader that Aeloth will merge with him. In this moment, the leader is killed by his own mistress who then claims the lead of the cult.
After having found all the sheets of notes, Zakk and Brodie go to the school building since they know there are amplifiers which allow them to play the hymn backwards. There, they meet Dion, Giles and Medina. As Brodie notices Zakks jacket in Medina's bag, Zakk's lie is revealed. Zakk tells Brodie he is not interested in Medina but simply wanted to have some fun to which Brodie responds with a punch to Zakk's face. A fight ensues between the two, which Zakk manages to win. He then decides to leave town.
Moments later, the remaining four are taken into custody by the members of the cult and brought into the house of Rikki Daggers in order to serve as sacrifice for Aeloth.
However, Zakk feels remorse for his friends and returns to them. He manages to free them and they attack the cult during their ritual for Aeloth. Brodie starts to play the Black Hymn backwards while the others defend him from the attacks by the cult members. In this fight, most of the cult members as well as Dion and Giles are killed. Brodie does not manage to play the hymn entirely before 3 AM, so Aeloth is able to enter the cult leader's body. Zakk then kills her, but since he is the most evil person amongst the remaining, Aeloth then takes possession of his body. Brodie realizes it's too late to complete the hymn, so instead he just plays heavy metal straight from his heart. The power of the music causes Zakk to collapse and temporarily transform back into his human body, but the respite is brief as Zakk can feel the demon trying to regain control. Zakk then urges Brodie to kill him in order to prevent the demon's resurrection, which Brodie eventually does.
A few months later, Brodie and Medina are a happy Death Metal couple in Greypoint. The scene ends with a friendly message by Zakk to Brodie which the latter hears through his record player. It seems Zakk is still melded with Aeloth in a parallel dimension.Milo Cawthorne as Brodie
James Blake as Zakk
Kimberley Crossman as Medina
Stephen Ure as Rikki Daggers
Tim Foley as Vadin
Sam Berkley as Dion
Daniel Cresswell as Giles
Nick Hoskins-Smith as David
Colin Moy as Uncle Albert
Jodie Rimmer as Aunt Mary
Howden took inspiration from his teenage years, in which he was a social outcast and fan of heavy metal music. The film won the 2013 Make My Horror Movie contest and received a NZ$200,000 prize to go toward production, which took place in mid-2014. Executive producer Ant Timpson cited Howden's "sheer enthusiasm and utter commitment" as to why it won.
Rotten Tomatoes reports that 88% of 25 critics gave the film a positive notice; the average rating is 6.4/10. The site's consensus states: "Deathgasm plumbs the blood-spattered depths of grindhouse gore with enough giddy glee to satisfy genre enthusiasts looking for a thrill." On Metacritic, the film has a 65 out of 100 rating, based on 10 critics, indicating "generally favorable reviews".
Dennis Harvey of Variety wrote that the script does not live up the vivid splatter effects, but the film's "consistent if undiscriminating high energy engenders a certain persuasive goodwill". Richard Whittaker of The Austin Chronicle wrote, "Shamelessly low-brow, reaching a beer-fueled gleeful high with a zombie-vs.-sex toys battle, it's a very metal tribute to the grand tradition of Kiwi splatter comedies." Matt Donato of We Got This Covered rated it 4/5 stars and wrote, "Deathgasm is the ultimate midnight movie (for metalheads especially), hitting on notes of horror insanity that blend face-melting riffage with equally outstanding practical effects."
At Bloody Disgusting, Brad Miska and Patrick Cooper reviewed the film, and both rated it four out of five stars. Miska called it "the most metal horror film ever", and Cooper said that it was "the movie the SXSW Midnighters category was created for". Drew Tinnin of Dread Central rated it 4/5 stars and wrote, "Deathgasm knows exactly what it is and where its heart is, giving genre fans a welcome return to heavy metal in horror without cutting back on any of the splatstick that New Zealand has become known for, for better or worse." Zach Gayne of Twitch Film wrote, "[T]he voice that shines through the hysterical dialogue and playfully comic editing, is so teenage, so punk, it makes a beat-to-death genre feel refreshing." Heather Wixson of Daily Dead rated it 5/5 stars and called it a "ridiculously fun and bombastic celebration of horror and heavy metal".
In early 2016, Walmart refused to sell Deathgasm in its current form. Walmart renamed the film to a more 'acceptable' title "Heavy Metal Apocalypse."
Nominated for a Fangoria Chainsaw Award, Best Makeup FX/Creature DesignToronto After Dark Film Festival
Best Feature Film – ANCHOR BAY ENTERTAINMENT AUDIENCE CHOICE AWARD WINNER: GOLD
Best Special Effects
Best Title Sequence
Best Film To Watch With A Crowd
Best Kill (Death by Sex Toy)
Best Screening Q&A
Knoxville Horror Film Festival
Best Director: Jason Lei Howden
Total Film Frightfest
Best Gore for Dildos & chainsaws
Festival de cine de Terror de Molins de Rei
Best Feature Film
Best Actor: Milo Cawthorne
Razor Reel Flanders Film Festival
HARD LINE Film Festival, Germany
L'Absurde Séance Film Festival
Arizona Underground Film Festival
A sequel, titled Deathgasm Part 2: Goremageddon, was revealed on 16 December 2015 to be in production.