Extreme metal is an umbrella term, somewhat loosely defined, for a number of related heavy metal subgenres that have developed since the 1980s. Though the term does not refer to any specific style or sound, it most commonly refers to music associated with thrash metal, black metal, death metal, and, arguably, doom metal. Though not well-known to mainstream music fans, extreme metal has influenced an array of musical performers inside and outside of heavy metal, and thrives in various devoted subcultures.