Heavy metal's first stirrings began amid blues-rock bands such as The Who and The Kinks. They used their guitar amplifiers to generate excessive amounts of feedback, as well as power guitar chords that later became a staple of heavy metal. Technological advances allowed them to record the reverbs and reproduce it on a record. The trend began to coalesce around a number of specific songs: the Beatles' "Revolution" and "Helter Skelter," The Yardbirds' "Think About It" and Iron Butterfly's "In-A-Gadda-Da-Vida," which featured a lengthy guitar solo.
The name "heavy metal" most likely derives from the band Steppenwolf, which scored a breakout hit on their first album in 1968. The song "Born to Be Wild" expounds upon the biker's lifestyle, stressing the freedom of the open road and the power of a motorcycle's engine, as well as the feelings they evoke in the singer. It includes the phrase "heavy metal thunder," which the genre eventually emulated.
Formal heavy metal first manifested in 1969 and 1970, with the release of several seminal albums. Foremost among them was Led Zepplin's self-titled first album, released in January 1969; a second album followed within a few months, cementing the band's intense, guitar-heavy sound. The bands Black Sabbath and Deep Purple both released albums in 1970, establishing the "classic" sense of sound. Black Sabbath's guitarist Tommy Iommi lost the tips of his fingers while working in a sheet metal factory as a teenager; unable to play complicated chords, he relied instead on power chords to establish Black Sabbath's sound.
As heavy metal developed in the 1970s, it took on aspects of excessive theatricality, marked by outrageous on-stage antics, costumes stressing black leather and spandex, excessive hair and sometimes even make-up. This stemmed in part from the growing punk movement, which adopted similar tactics as a form of social rebellion. They worked well with heavy metal and were quickly adopted by artists such as Ozzy Osbourne and Alice Cooper.
By the 1980s, heavy metal had become decidedly mainstream. A second wave of British bands emerged a few years earlier, topped by the likes of Iron Maiden and Def Leppard. American bands developed in the Los Angeles area, including Quiet Riot, Van Halen and Mötley Crüe, cementing both the heavy metal sound and allowing it to develop in a new and different direction.