Well, it's not a song, but the term "Heavy Metal" was actually coined by the Beat writer William S. Burroughs (author of Naked Lunch).
From Wikipedia:
"An early use of the term in modern popular culture was by counter-culture writer William S. Burroughs. In his 1962 novel The Soft Machine, he introduces the character "Uranian Willy, the Heavy Metal Kid". His next novel in 1964 Nova Express, develops this theme further, heavy metal being a metaphor for addictive drugs:
"With their diseases and orgasm drugs and their sexless parasite life forms - Heavy Metal People of Uranus wrapped in cool blue mist of vaporized bank notes - And the Insect People of Minraud with metal music..."
Burroughs, William S, (1964). Nova Express. New York: Grove Press. p. 112
Interesting tidbit....
ND