In England, this was called "Get It On (Bang A Gong)." The title was changed on the American release so it would be less offensive.
This is about sex, but most of the imagery is vague enough that many people did not pick up on it.
This is a great example of "Glam Rock." There was nothing all that distinctive about glam music, but it was characterized by the outrageous, often effeminate costumes the performers wore and the very theatrical stage shows.
The last line, "Meanwhile, I'm still thinking..." was a nod to a Chuck Berry song called "Little Queenie," which contains the same lyric and inflection.
In the US, this was the only hit for T-Rex. They had several hits in England before glam rock fell out of favor.
Mark Volman and Howard Kaylen sang backup vocals. Known as "Flo and Eddie," Volman and Kaylen were members of The Turtles. (thanks, Paul Miller - Chandler, AZ)
The band released this a year after they shortened their name. They had been Tyrannosaurus Rex.
After falling from fame a few years after this came out, lead singer Marc Bolan was killed in 1977 when his girlfriend crashed their car into a tree.
In 1985, the "Supergroup" Power Station, which included Robert Palmer and members of Duran Duran, released this as a single. They used the original title on both sides of the Atlantic: "Get It On" (thanks, Brad Wind - Miami, FL)
Marc Bolan took his name from Bob Dylan... BO from Bob and LAN from Dylan. (thanks, Bob - Atlanta, GA)
Blondie recorded a live version for their 1978 Parallel Lines album. (thanks, Chrissy - Manchester, England)