Unlike other bands associated with the 1990s alternative music movement, Primus emerged from a mostly heavy metal background, with Claypool and LaLonde previously a part of the 1980s Californian thrash metal underground. Kirk Hammett, guitarist of Bay Area thrash metal band Metallica, remarked in a 1991 interview that Primus are "unique, they're a square peg in a round hole". The music of Primus has been described as "thrash-funk meets Don Knotts, Jr." and "the Freak Brothers set to music". Also, Primus has been categorized as alternative rock, alternative metal, experimental rock, funk rock, funk metal, progressive rock, and "thrash-funk". Regarding the band's genre, Claypool stated in 1991 "We've been lumped in with the funk metal thing just about everywhere. I guess people just have to categorize you". "MTV" suggests that Primus is "a post-punk Rush spiked with the sensibility and humor of Frank Zappa". Les Claypool himself once described their music as "psychedelic polka." "Spin" have labelled Primus as "pranksters" and, in 1995, as an "unlikely gold-selling white trash purveyor of hard-ass pinballing funk metal".