Nu metal is a sub-genre of Heavy metal, which has hit mainstream popularity since the late 1990's. The attributes of Nu metal change from band to band, but can include electronic, funk, glam rock, gothic rock, grunge, hardcore pop, hip hop, industrial rock, jazz, post punk and synthpop.
A common theme in the lyrics for Nu metal is that it focuses on pain and personal alienation, for example Limp Bizkit's Results may vary, Linkin Park's Minutes to Midnight and Papa Roach's Getting away with murder.
Nu metal, unlike most other types of metal, lacks guitar solo's. Instead it focuses on the rythem in the song.