Steel monkey is a nickname used to refer to workers on high scaffolding

Scaffolding

Scaffolding is a temporary structure used to support people and material in the construction or repair of buildings and other large structures. It is usually a modular system of metal pipes or tubes, although it can be from other materials...

 or other aerial construction rigs. It is possible that the term developed from the similar term rigging monkey

Rigging monkey

Rigging Monkey refers to a crewmember of a sailing vessel whose primary responsibility is to climb the mast, usually with the assistance of a boatswain's chair, to work on the rigging of the ship....

, used on large sailing ships to refer to crewmembers whose responsibilities included climbing the ship's mast.

Other uses

The term has been used as the title of a song, "Steel monkey", by rock band Jethro Tull

Jethro Tull (band)

Jethro Tull are a British rock group formed in 1967. Their music is characterised by the vocals, acoustic guitar, and flute playing of Ian Anderson, who has led the band since its founding, and the guitar work of Martin Barre, who has been with the band since 1969.Initially playing blues rock with...

.

The term also refers to a mixed drink, composed of Steel Reserve malt liquor and orange juice, made popular by the rap group Battlecougar.