Cave In formed in Methuen, Massachusetts in 1995, beginning as a metalcore act before undergoing one of the more dramatic stylistic evolutions in underground heavy music, shifting from the technical aggression of Until Your Heart Stops (1998) to the sprawling space-rock of Jupiter (2000). They signed to RCA Records and released the alternative rock-oriented Antenna in 2003, then went on hiatus in 2006 before reforming in 2009 and returning to heavier territory. The band remains active and is regarded as a key bridge between hardcore, progressive rock, and post-metal.

Ceremony formed in Rohnert Park, California in 2005, releasing their debut EP Ruined on Malfunction Records that same year and quickly establishing themselves in the California hardcore underground with a raw powerviolence-adjacent approach. Over subsequent albums, the band underwent a deliberate stylistic migration through 1980s-influenced hardcore, garage rock, and post-punk, exploring a range of sounds while retaining an underlying confrontational energy. They have released six studio albums and remain active.

City of Caterpillar formed in Richmond, Virginia in 2000, becoming one of the central acts in the early American screamo movement alongside Pg. 99 and Majority Rule, building lengthy compositions that shifted between near-ambient quiet and shattering emotional climaxes. The band released a self-titled full-length and split releases before disbanding in 2003, with the recordings gaining wider recognition in subsequent years as touchstones of the form. The band reunited in 2016 and released their second album Mystic Sisters in 2022.

Cloakroom formed in Indiana in June 2012, developing a sound that drew equally from shoegaze's textured reverb, 1990s slowcore melancholy, and hardcore's physical weight, with reference points including Hum and Red House Painters. Their debut Further Out appeared in 2015, and the band went on to release Time Well (2017) and Dissolution Wave (2022) on Relapse Records. Their 2025 album Last Leg of the Human Table continued their exploration of heavy, introspective guitar music.

Orlando thrash metal project from the Florida underground.

Birmingham, Alabama's Haste formed in 1995 and occupied a space where post-hardcore, metalcore, and emo intersected. The band released three albums — Pursuit in the Face of Consequence (1999), When Reason Sleeps (2001), and The Mercury Lift (2003) — before disbanding in 2007. The Mercury Lift in particular drew comparisons to the atmospheric post-hardcore of Quicksand and Hum, and the band is remembered as a defining act of the early 2000s regional heavy music scene.

Wakrat is a Los Angeles trio formed in 2015 by Tim Commerford, bassist of Rage Against the Machine, alongside French guitarist Laurent Grangeon and Swiss drummer Mathias Wakrat, whose surname provided the band's name. The band plays aggressive, politically charged punk and alternative metal with clear DNA from Commerford's previous work, and released their self-titled debut album in 2016 after debuting live at the Viper Room in September 2015.

ÆGES is a Los Angeles, California post-hardcore and alternative metal band formed in 2011, featuring members drawn from Pelican, -16-, and The Rise. The band combines heavy, riff-forward guitar work rooted in 90s post-hardcore with melodic desert rock hooks and doom-inflected arrangements. Their 2014 album Above and Down Below is the centerpiece of their catalog, demonstrating an approach that draws from Quicksand, Soundgarden, and Queens of the Stone Age without directly imitating any of them. Their output is relatively limited in volume but appreciated within the underground heavy rock community for its density and craft.