A type of rock and roll music characterized by heavily distorted guitars, powerful drumming, and vocals often performed at an intense screaming level. Very counter culture, aggressive, and nonconformist. Usually played at very high volume.
It was made possible by advancements in electronic amplification in the 1960s.
In music, the phrase originated in the lyrics to the 1968 song "Born To Be Wild" by Steppenwolf:
"I like smoke and lightning
Heavy metal thunder
Racin' with the wind
And the feelin' that I'm under"
William S. Burroughs used the term in a novel a few years earlier as a metaphor for drug use, but did not apply it to music.
Heavy metal bands include:
Garth Brooks wanted to be a Heavy Metal musician, but he's too lightweight