Nu metal (also known as nü-metal, aggro-metal, neo-metal or new metal) is a subgenre of heavy metal. It is a fusion genre which combines elements of alternative metal with other genres, including grunge and hip hop.

Rock bands of the 1980s and 1990s including Faith No More, Red Hot Chili Peppers, Jane's Addiction, Nirvana, Tool and Rage Against the Machine have been identified as laying groundwork for the development of nu metal by popularising elements of the genre, such as combining aggressive riffs with pop structures and drawing influence from a variety of genres within and outside of heavy metal. Another band that has been frequently credited for nu metal's development is post-hardcore outfit Fugazi. This has been confirmed by Limp Bizkit frontman Fred Durst who, in an interview, said that Fugazi is "one of [his] all time favorite bands." Linkin Park also cite Fugazi as an influence, particularly the songs "In The End" and "Numb," which vocalist Chester Bennington says were the band's personal attempts at writing a Fugazi song.

Bands associated with nu metal derive influence from a variety of diverse styles, including electronic music, funk, glam metal, gothic rock, grunge, hardcore punk, hip hop, industrial metal, jazz, post-punk and synthpop. Nu metal also derives influences from multiple sub-genres of heavy metal including rap metal, funk metal, alternative metal and thrash metal.

Nu metal music is mostly syncopated and based on riffs. Mid-song breakdowns and lack of solos contrasts it with other metal sub-genres. Another contrast with other metal sub-genres is its emphasis on rhythm, tending to more elements of groove metal in rhythm. Similarities with other heavy metal sub-genres include its use of common time, distorted guitars, power chords and note structures primarily revolving around Dorian, Aeolian or Phrygian modes.
Many nu metal bands use seven-string guitars over traditional six-string guitars. Seven-string guitars, which are sometimes downtuned to increase heaviness, resulted in bass guitarists using five-string and six string instruments. DJs are also sometimes used for additional rhythmic instrumentation such as music sampling, scratching and electronic backgrounds.

Nu metal vocal styles range between melodic singing, rapping, screaming and death growling, sometimes using multiple of these styles within one song. The lyrics of many nu metal bands focus on pain and personal alienation rather than the themes of other metal subgenres. Q Magazine stated that many of the genre's "leading lights [focused on] abandonment issues they should have left behind on their first day of big school".
Nu metal uses the traditional pop structure of verses, choruses and bridges, contrasting it with other metal genres such as thrash and death metal. Nu metal fashion can include baggy shirts, cargo pants, sweatpants, body piercings, tattoos, and in some cases jumpsuits and sweatsuits.