beryllium vs metallic element

beryllium and metallic element both are nouns.

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

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

beryllium: a light strong brittle grey toxic bivalent metallic element
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 beryllium include metal.

beryllium (noun)	metallic element (noun)
a light strong brittle grey toxic bivalent metallic element	any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.