>>127419594 (OP)
It's the end result of the steadfast commercialization and fusion of heavy music: Rap Rock, Hard Alternative/Grunge, Industrial Rock/Metal, Funk Metal, Groove Metal and even Hardcore Punk were popular on MTV from the late '80s up until '94. By the time Korn dropped their first album, all those other genres fell by the wayside and Nu-Metal rose to the top.
While bands seldom differentiated in lyrics covering pain, angst, destruction and misanthropy, most of them sounded worlds apart from one another. Korn, Limp Bizkit, Soulfly or Static-X reveled in bravado, impulsive and tribalistic aggression while Slipknot or Marilyn Manson hearkened to '70s Shock Rock with '90s sensibilities and aesthetics. Korn took cues from Faith No More and Helmet while Slipknot looked up to Mr. Bungle. Deftones had a more Post-Hardcore meets Hip-Hop undertone to their Nu-Metal sound. Towards the twilight of the genre's life, Linkin Park was introspective in their lyrics and focused more on Electronic, Trip-Hop and even Ambient atmospheres with their sound.
Separating those bands from their influences was their willingness to conform and return to machismo thanks to the Hip-Hop and Hardcore influences. Alternative bands were often quirky, elegant and socially progressive, thus politically correct. Nu-Metal took the opposite approach with more bands conforming to a tough-as-nails working class style. With minor exception, those guys were looking to throw down if you so much as gave them an awkward look.
To me, these bands were directly responsible for Nu-Metal's genesis or were influential, but not necessarily Nu-Metal: Pantera, Helmet, Prong, 24-7 Spyz, Living Colour, Fishbone, Deftones, Mordred, RATM, Tool, Infectious Grooves, Mr. Bungle, Faith No More, '90s Sepultura, Alice in Chains, Acid Bath, Godsmack, Body Count, White Zombie, L.A.P.D., Korn, Biohazard, Ministry, Nine Inch Nails, Marilyn Manson, Skinlab, Slipknot, Soulfly, Powerman 5000, P.O.D. and many others.