bullion vs precious metal

bullion and precious metal both are nouns.

Word	Noun	Adjective	Verb	Adverb
bullion	Yes	No	No	No
precious metal	Yes	No	No	No

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

bullion: a mass of precious metal
precious metal: any of the less common and valuable metals often used to make coins or jewelry

bullion (noun)	precious metal (noun)
gold or silver in bars or ingots	any of the less common and valuable metals often used to make coins or jewelry
a mass of precious metal