on fire vs aflame

on fire and aflame both are adjectives.

Word	Noun	Adjective	Verb	Adverb
on fire	No	Yes	No	No
aflame	No	Yes	No	No

As adjectives, on fire and aflame are synonyms defined as:

Other synonyms of on fire include ablaze, afire, aflare, alight.

on fire (adjective)	aflame (adjective)
lighted up by or as by fire or flame	lighted up by or as by fire or flame
	keenly excited (especially sexually) or indicating excitement