Bayān imkān al-mushabbah is used when the subject is credited with a quality so exceptional that a listener considers it unlikely or seemingly impossible. The model supplies a recognizable parallel in which an unexpected outcome is possible.
The comparison reduces the listener's feeling of impossibility: a remarkable transformation or distinction in one familiar case makes a comparable claim in another less difficult to conceive.
The primary task is not to measure intensity or decorate a description, but to establish the conceivability of the claim.