Majāz mursal — the semantic relation is something other than resemblance.
Istiʿārah — the relation is resemblance, intentionally used to support the transferred description.
For majāz mursal, the main analytical task is to identify the type and direction of the connection: cause/effect, part/whole, earlier/later condition, place/occupant, or instrument/result. With metaphor, one additionally analyzes the two compared things, the original and target meanings and the distinctive contextual indication.
Compare:
“We grazed the rain” — rain to vegetation, mursal.
“I saw a lion shooting” — lion to brave human, metaphor.
The following lesson develops metaphor's distinct structural classifications in detail.