aflame vs on fire

aflame and on fire both are adjectives.

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

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

Other synonyms of aflame include ablaze, afire, aflare, alight.

aflame (adjective)	on fire (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