Reine Barb, membre de la royauté hard-rock, aidée de son père Roi Thrash, veut détruire tous les autres genres de musique pour laisser le rock régner en maître. Le destin du monde en jeu, Poppy et Branch, accompagnés de leurs amis – Biggie, Chenille, Satin, Cooper et Guy Diamond – partent visiter tous les autres territoires pour unifier les Trolls contre Barb, qui cherche à tous les reléguer au second-plan. Poppy and Branch discover that they are but one of six different Troll tribes scattered over six different lands devoted to six different kinds of music: Funk, Country, Techno, Classical, Pop and Rock. Their world is about to get a lot bigger and a whole lot louder. A member of hard-rock royalty, Queen Barb, aided by her father King Thrash, wants to destroy all other kinds of music to let rock reign supreme. With the fate of the world at stake, Poppy and Branch, along with their friends, set out to visit all the other lands to unify the Trolls in harmony against Barb, who's looking to upstage them all.