Collocations for junk - noun

old
sculptures made from old junk and scrap metal

useless

bit, piece
There were bits of junk lying around.

heap, pile

lie about (esp. BrE), lie around

shop
room
They cleared out the junk room to make a tiny bedroom.

heap, pile
material
He made the boat out of junk materials.

food
He sits around eating junk food all day.

email, mail
bond (= high-risk investment)
science (= invalid)
The company described the report as ‘junk science’.