rubbish vs junk

rubbish and junk both are nouns.

Word	Noun	Adjective	Verb	Adverb
rubbish	Yes	No	Yes	No
junk	Yes	No	Yes	No

As nouns, junk is a hyponym of rubbish; that is, junk is a word with a more specific, narrower meaning than rubbish:

Other hyponyms of rubbish include scrap metal, debris, detritus, dust, rubble, litter.

rubbish (noun)	junk (noun)
nonsensical talk or writing	any of various Chinese boats with a high poop and lugsails
worthless material that is to be disposed of	the remains of something that has been destroyed or broken up

rubbish (verb)	junk (verb)
attack strongly	dispose of (something useless or old)