archangel vs Michael

archangel and Michael both are nouns.

Word	Noun	Adjective	Verb	Adverb
archangel	Yes	No	No	No
Michael	Yes	No	No	No

As nouns, Michael is a hyponym of archangel; that is, Michael is a word with a more specific, narrower meaning than archangel:

archangel: an angel ranked above the highest rank in the celestial hierarchy
Michael: (Old Testament) the guardian archangel of the Jews

Other hyponyms of archangel include Gabriel, Raphael.

archangel (noun)	Michael (noun)
an angel ranked above the highest rank in the celestial hierarchy	(Old Testament) the guardian archangel of the Jews
a biennial cultivated herb; its stems are candied and eaten and its roots are used medicinally