Iron Maiden are an English heavy metal band formed in Leyton, East London, in 1975 by bassist and primary songwriter Steve Harris. Although fluid in the early years of the band, the line-up for most of the band's history has consisted of Harris, lead vocalist Bruce Dickinson, drummer Nicko McBrain, and guitarists Dave Murray, Adrian Smith and Janick Gers. As pioneers of the new wave of British heavy metal movement, Iron Maiden released a series of UK and US Platinum and Gold albums, including 1980's debut album, 1981's Killers, and 1982's The Number of the Beast – its first album with Bruce Dickinson, who in 1981 replaced Paul Di'Anno as lead singer. The addition of Dickinson was a turning point in their career, establishing them as one of heavy metal's most important bands. The Number of the Beast is among the most popular heavy metal albums of all time, having sold almost 20 million copies worldwide.

Heavy metal is a genre of rock music that developed in the late 1960s and early 1970s, largely in the United Kingdom and United States. With roots in blues rock, psychedelic rock and acid rock, heavy metal bands developed a thick, monumental sound characterized by distorted guitars, extended guitar solos, emphatic beats and loudness.