Nu-metal I considered something a bit different. Slipknot are still weirdly huge and their last album went to number 1, though obviously new bands in that genre don't go anywhere anymore.
Nu-Metal (Nü-Metal?) has always been a fascinating case study in the evolution of heavy music, especially once it becomes commercially viable. The genre stood at the vertex of Rap Rock, Hard Alternative/Grunge, Industrial Rock/Metal, Funk Metal, Groove Metal and even Hardcore Punk (to a much lesser extent), all popular on MTV from the late '80s up until '94. By the time Korn dropped their first album, all those genres fell by the wayside into the background 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. Bands like Korn, Limp Bizkit, Soulfly or Static-X reveled in bravado, impulsive and tribalistic aggression while Slipknot or Marilyn Manson hearkened to Shock Rock. Korn took cues from Faith No More and Helmet while Slipknot looked up to Mr. Bungle. Deftones initially 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.
Twas an eclectic genre, but 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.
Bands directly responsible for its genesis or 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, Godsmack, Body Count, White Zombie, L.A.P.D., Korn, Biohazard, Ministry, Nine Inch Nails, Marilyn Manson, Skinlab, Slipknot, Soulfly, Mushroomhead, One Minute Silence, Powerman 5000, P.O.D. and countless others.