Metalcore is a slippery concept. A relatively new genre category, dating from the early 2000s, it provokes wide disagreement about what counts as metalcore and arguments within metal scenes about its legitimacy. This chapter provides an overview of metalcore as an ‘abject genre’, a useful shorthand term for nu metal, screamo, and a variety of core subgenres that have been widely criticised by metal fans. Beginning with commonalities that metalcore shares with other abject genres – some mass popularity, stylistic alterations of traditional metal traits that detractors view as simplified dilutions, quotidian rather than supernatural lyrics, and associations with marginalized categories of identity – I then outline diverse historical accounts by other authors to argue for a more complex view of chronological and conceptual boundaries than an individual narrative might allow. Finally, an analysis of Currents’ ‘Silence’ (2017) provides an example of metalcore as an amalgamation of stylistic qualities from multiple sources. I conclude with thoughts on the utility of abject genres as a concept for reception histories and the potential for metalcore’s complexity as a genre to teach broad lessons about genre in popular music.