Ive been listening to nu metal for almost 2 years now and i have explored a fair bit of lesser known and some, what i consider, underground bands (no specific order).
My So Called Life - From Zero: I think this album gets really overshadowed by one nation under. in someway i understand since the band leaned more on the softer side in this one, but in my opinion its as good of an album as the first one. I really recommend "My So Called Life" and "Believe"
Mind Justice - From Zero: this is a specific song. it wasnt on the two full length albums, but rather on their self release (green cd), the one nation under promo sampler and maybe some other promo material. its an extremely good song which showcases the groove of the band and its just a banger
Lost Angel - 3rd Strike: nothing other to say than 10/10 album from start to finish, the cover of "Paranoid" by Black Sabbath is the best I ever heard and they put their own twist on it. Rest in Peace Jim 🕊️
Beyond The Calm Of The Corridor - The Blank Theory: Amazing Album with good narrative, i really enjoy the vocals and the songs are really catchy. I recommend "Invisible", "Back Of My Mind" and "Killing Me"
Various Material - Brik: The EPs and albums as a whole didnt stand out to me as a whole, but some songs are crazy good, their vibe is really dark and catchy. I recommend "Leave Me Alone", "Betrayed" (Album Version from Goodbye) and "Held Inside"
Darkhorse - Crazy Town: one or two songs are ok-ish, but the majority are really overlooked bangers. I strongly recommend "Change", "Drowning" and "Waste of my Time". I think the bands other material is generally overlooked cause of "Butterfly". Rest in peace Shifty, Adam and Rust 🕊️
Self Titled - Of That Nature: i dont really know if they are widely considered nu metal, but imo they give of that vibe and i would at least consider them nu-adjacent. really incredible new comers, they really put a twist on their music which other new bands dont. I recommend "Chinese Molasses" and "Poison Berry Pie"
Laced - Reveille: Really catchy political and agressive songs, really important in the present day. i dont know if i recall correctly but the band itself has said they dont consider themselves nu metal, but correct me if im wrong. nontheless, they are definetly part of that early 2000s wave of metal. I strongly recommend "Perfect World" and "Untied"
Self Titled - SORE (Source of Raw Energy): Really good album, good harmony between the vocalists and great guitar sound. the songs are catchy and i really like the DRP's screams. although some people told me they didnt really like the vocals or they take some getting used to. but imo its just good music. I recommend "Position", "Dark December" and "When In Rome"
Start a War and Cult of Static - Static-X: I think Static-X is generally a somewhat overlooked band by the mainstream. i heard some people say they were bigger back then and that they were well known, but it doesnt seem like that nowadays. maybe it has to do with the loss of Wayne (Rest in Peace🕊️) that people dont consider it "the real" static x anymore. Anyway, i think Start A War is their best work by far, the songs are catchy, the narrative is excellent and the vocals are on point, one of my favorite albums from all of nu. I recommend "Im the One", "Pieces", "Set It Off" and "Pieces". About Cult Of Static, they definetly leaned more on the industrial side on this one, but its a very overseen album, really unique. I recommend "Z28", "Tera-Fied" and "Lunatic".
Life - Dope: 10/10 all the way through, some really emotional songs on this record. they topped their debut with this one, one of my favorite albums. I recommend "Nothing (Why)", "What About", "Crazy", "Now Or Never" and "Slipping Away"
Encore! - Thumb: Really underrated band, political narrative which has importance in modern day, nothing much to say. I recommend "Red Alert '96" and "Victim Of Your Lies"
Better In Two Weeks - Wurkt: Extremely crazy good music, nice groove and nice vocals, nothing to complain. I recommend "Foreskin" and "Faithful"
Other bands that are worth to mention: Mainstay, Nervepitch, Slodust, Incubus (nu metal era), Headplate and Drowning Pool.
Some more famous bands but not in the big 5 are: Sevendust with Animosity and Seasons, Saliva with Every Six Seconds and Mudvayne with L.D. 50.
Let me know what you think and recommend me some of your deep cuts, cheers