heroic meter vs epic poem

heroic meter and epic poem both are nouns.

Word	Noun	Adjective	Verb	Adverb
heroic meter	Yes	No	No	No
epic poem	Yes	No	No	No

As nouns, epic poem is a hypernym of heroic meter; that is, epic poem is a word with a broader meaning than heroic meter:

heroic meter: a verse form suited to the treatment of heroic or elevated themes; dactylic hexameter or iambic pentameter
epic poem: a long narrative poem telling of a hero's deeds

Other hypernyms of heroic meter include epic, epos, heroic poem.

heroic meter (noun)	epic poem (noun)
a verse form suited to the treatment of heroic or elevated themes; dactylic hexameter or iambic pentameter	a long narrative poem telling of a hero's deeds