tinplate vs sheet metal

tinplate and sheet metal both are nouns.

Word	Noun	Adjective	Verb	Adverb
tinplate	Yes	No	No	No
sheet metal	Yes	No	No	No

As nouns, sheet metal is a hypernym of tinplate; that is, sheet metal is a word with a broader meaning than tinplate:

tinplate: a thin sheet of metal (iron or steel) coated with tin to prevent rusting; used especially for cans, pots, and tins
sheet metal: sheet of metal formed into a thin plate

tinplate (noun)	sheet metal (noun)
a thin sheet of metal (iron or steel) coated with tin to prevent rusting; used especially for cans, pots, and tins	sheet of metal formed into a thin plate