noble metal vs metallic element

noble metal and metallic element both are nouns.

Word	Noun	Adjective	Verb	Adverb
noble metal	Yes	No	No	No
metallic element	Yes	No	No	No

As nouns, metallic element is a hypernym of noble metal; that is, metallic element is a word with a broader meaning than noble metal:

noble metal: any metal that is resistant to corrosion or oxidation
metallic element: any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.

Other hypernyms of noble metal include metal.

noble metal (noun)	metallic element (noun)
any metal that is resistant to corrosion or oxidation	any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.