From Nookipedia, the Animal Crossing wiki
K.K. Metal is a K.K. Slider song. It has a hardcore, super fast-paced metallic beat to it with a heavy metal guitar and a rocker's drum kit. First comes verse one, then the chorus after that, then it repeats. It is a shorter K.K. song. Bella, Big Top, Groucho, Tex and Sprocket (in Animal Crossing: New Leaf - Welcome amiibo) play this song in their homes.