In the 1980s, various bands in both hardcore punk and metal scenes worldwide were crossing over. In terms of metalcore, the mid-1980s New York hardcore scene in particular is arguably the most influential. The likes from this scene, such as Cro-Mags, Leeway, and Sheer Terror, took inspiration from popular metal bands of the time such as Venom, Motörhead, Celtic Frost, Metallica, and Slayer. At this point, "metalcore" was used to describe some of these bands. In the early 1990s, Starkweather, Integrity, Ringworm, Earth Crisis, and Rorschach have expanded this fusion in their influential recordings, and, by the time the mid-1990s have arrived, many different metalcore bands took note and started to push the genre into more extreme territories.
In West Flanders, Belgium, a vegan straight edge scene called H8000 was spearheaded by the likes of Congress and Liar. These bands heavily incorporated aspects of death metal and thrash metal, musically aligning themselves with contemporaries outside the scene such as All Out War, Merauder, and Kickback. Meanwhile, in Bremen, Germany; Acme, Systral, and Carol played a dissonant and fragmented metalcore style heavily inspired by Rorschach. Additionally, Deadguy, Lethargy, and Candiria experimented with a wide array of genres, mainly noise rock, post-hardcore, technical thrash metal, technical death metal, and jazz fusion, establishing mathcore in the process before Botch, The Dillinger Escape Plan, and Converge expanded and popularized it years later.
During the late 1990s, a style of melodic metalcore was popularized by Massachusetts bands Shadows Fall, Killswitch Engage, and Unearth, who were mainly inspired by the Gothenburg melodic death metal scene. Meanwhile, on the other end of the melodic metalcore spectrum, bands like Poison the Well and Shai Hulud were also releasing their own pioneering records. By the time the 2000s came around, both of these styles' accessibility paved the way for a large number of bands, some even polishing the sound for wider commercial appeal.
However, while these bands are popular and helped lay the development of the (separate) modern metalcore scene, there are others that kept closer to the genre's traditional roots. For example, bands like Cursed, Trap Them, and Oathbreaker led the development of dark metalcore; a distinctively aggressive form of the genre that emphasizes a dark, gritty, and ominous atmosphere. Additionally, other bands such as early Cave In, Keelhaul, and early Mastodon utilized a mathcore-derived style by mostly forgoing its harsh dissonance, and, instead, using off-kilter riffing and progressive-driven song structures.
In recent years, traditional metalcore bands such as Knocked Loose, Code Orange, and Jesus Piece have gained large amount of following, indicating a renewed interest towards the genre as a whole. .