americium vs metallic element

americium and metallic element both are nouns.

Word	Noun	Adjective	Verb	Adverb
americium	Yes	No	No	No
metallic element	Yes	No	No	No

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

americium: a radioactive transuranic metallic element; discovered by bombarding uranium with helium atoms
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 americium include metal.

americium (noun)	metallic element (noun)
a radioactive transuranic metallic element; discovered by bombarding uranium with helium atoms	any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.