type metal vs type slug

type metal and type slug both are nouns.

Word	Noun	Adjective	Verb	Adverb
type metal	Yes	No	No	No
type slug	Yes	No	No	No

As nouns, type slug is a hyponym of type metal; that is, type slug is a word with a more specific, narrower meaning than type metal:

type metal: an alloy of tin and lead and antimony used to make printing type
type slug: a strip of type metal used for spacing

Other hyponyms of type metal include slug.

type metal (noun)	type slug (noun)
an alloy of tin and lead and antimony used to make printing type	a strip of type metal used for spacing