Heavy metal (or simply metal) is a genre of rock music that developed in the late 1960s and early 1970s, largely in the United Kingdom. With roots in blues rock, psychedelic rock, acid rock, and occult rock. The bands that created heavy metal developed a thick, massive sound, characterized by highly amplified distortion, extended guitar solos, emphatic beats, and overall loudness. Heavy metal lyrics and performance styles are sometimes associated with aggression and machismo.
In 1968, three of the genre's most famous pioneers, Led Zeppelin, Black Sabbath and Deep Purple were founded. Though they came to attract wide audiences, they were often derided by critics. During the mid-1970s, Judas Priest helped spur the genre's evolution by discarding much of its blues influence; Motörhead introduced a punk rock sensibility and an increasing emphasis on speed. Beginning in the late 1970s, bands in the new wave of British heavy metal such as Iron Maiden and Saxon followed in a similar vein. Before the end of the decade, heavy metal fans became known as "metalheads" or "headbangers".
During the 1980s, glam metal became popular with groups such as Mötley Crüe, Poison and Def Leppard. Underground scenes produced an array of more aggressive styles: thrash metal broke into the mainstream with bands such as Metallica, Slayer, Megadeth, and Anthrax, while other extreme subgenres of heavy metal such as death metal (with bands such as Death, Possessed, and Obituary) and black metal (with bands such as Mayhem, Bathory, and Immortal) remain subcultural phenomena. Since the mid-1990s popular styles have further expanded the definition of the genre. These include groove metal (with bands such as Pantera, Sepultura, and Lamb of God) and nu metal (with bands such as Korn, Slipknot, System of a Down, and Linkin Park), the latter of which often incorporates elements of grunge and hip hop.