Enough time has past that we can look back and analyze the Nu Metal era... I even made a playlist to accompany what I think are the best entries in the genre and from the best five years of the genre's life.
The early to mid-90s really gave us an interesting moment in music. Gen X was busy popularizing college rock radio with their interest in grunge and alternative, but gangster rap was also starting gain popularity as well. There had been some rap-rock hybrids in the 80s, but the music never took off. While Nu Metal doesn't necessarily have to be mixture of rap-rock, some of the most notable bands to come out of the TRL generation definitely popularized the mixture, and definitely influenced their peers to include a lot of the signature hooks, mixing rap and rock together or employing the use of turntables; Limp Bizkit, Linkin Park, Deftones--to a certain extent, they are not exactly "Nu Metal," but I might get into that later on--Korn, P.O.D., System of a Down, Godsmack, Marilyn Manson, etc. By virtue of a pure dictionary definition, Nu Metal is by all rights a bit of a nerdy fusion genre with a lot of navel-gazing because it takes from so many other genres. It's interesting to me that it became as popular as it did. Without question, the height of Nu Metal was 1998-2003. It may still have been around by the time I graduated high school, but I wasn't listening to it any more by the time I was a senior in 04, nor was it music that really captivated the masses prior to 98. It took around 3-4 years for it to develop and gain traction through albums like Korn's Life is Peachy. Not to mention, TRL the way we remember it with Carson Daly was as shell of its former self by the time he stepped down in 2003. It is interesting though that I associate TRL and Carson Daly's period of hosting that show as the direct and proximate 5 years that played host to the best the Nu Metal genre had offer.