Metalhead Hunter Sylvester, portrayed by Adrian Greensmith, is passionate about music and often jams with his best friend, the anxious Kevin Schlieb, played by Jaeden Lieberher. While Kevin is limited to playing just one drum in the school's marching band, he expresses a desire to learn the full kit. During band practice, Kevin witnesses Emily, a troubled Scottish student played by Isis Hainsworth, having a breakdown as she quits due to her clarinet struggles. Meanwhile, Hunter and Kevin face financial hurdles as they need $1,000 to purchase a complete drum set.
Their day takes a turn when Kevin insists on attending a party hosted by Clay Moss played by Noah Urrea. There, Kevin attempts to fit in while Hunter feels out of place. The party goes awry with Kevin drunkenly flirting with Kendall played by [Analesa Fisher], while Hunter finds himself clashing with the school jock, Rocky "Skip" Hoffman, who has a knack for bullying them.
The duo’s fortunes shift when Hunter learns about an upcoming "Battle of the Bands," igniting his ambition for fame and pushing him to sign up their band, humorously named Skullfucker. Determined to win, Hunter takes a reckless step by swiping his dad's AMEX card to splurge on band gear, including a drum kit for Kevin. During practice, Kevin discovers Emily's hidden talent as a skilled cellist, leading to a budding romance between them as he shares a metal playlist assigned by Hunter.
However, Hunter's fixation on winning creates tension; he rudely dismisses Emily as a potential bassist for their band, claiming she doesn't match their image. This strains their friendship as Kevin begins dating Emily after a heartfelt apology, unknowingly stirring jealousy in Hunter, who fears Emily will derail their band's success. Meanwhile, Clay, who invites Kevin to join his band, finds himself in a complicated situation when Mollycoddle's drummer goes to rehab.
Tensions escalate as Hunter mocks Emily during class, leading her to confront him and inadvertently damaging his guitar. This confrontation culminates in a fallout between him and Kevin, forcing Kevin to join Mollycoddle and perform at a family wedding, while Hunter's attempts to reconcile lead him to criminal mischief and arrest.
As both friends navigate their shifting loyalties, Kevin is confronted by fantastical representations of his conscience in the form of heavy-metal icons. Their guidance helps him realize his true feelings for Emily and the importance of his friendship with Hunter. In a twist of fate, Hunter finds himself in a rehab run by Dr. Troy Nix, brilliantly portrayed by Joe Manganiello, who shares his own struggles with addiction and underscores the value of friendship and overcoming personal demons.
After a daring escape from rehab, Hunter and Kevin go to seek Emily's forgiveness and invite her to join them as their cellist. At the Battle of the Bands, Kevin decides to bow out of Mollycoddle to make space for their new drummer, only for Emily to step in at the last moment, transforming their group into Skullflower. Although chaos ensues when Skip's drunken antics lead to an injury for Hunter, their performance is a resounding success, leaving them as viral sensations despite not winning the contest.
In an uplifting conclusion, the trio—Kevin, Emily, and a recovering Hunter—find themselves back in the basement, overcoming their struggles and ready to take on new challenges as a band, united by a shared passion and newfound camaraderie.
