Songs that aren't actually on movie soundtracks but instantly make you think of a generic movie moment that they would be perfect for. Or what the song looks like as a scene in a movie.
E.g. several songs (esp. The Twist) from Frightened Rabbit's Midnight Organ Fight look like the moment that mismatched and mutually (if superficially) hostile man and woman suddenly realise that they fancy each other something rotten and head on back to his/her/hotel room for steamy yet oh-so-tender sex scene.
"Olympians" by Fuck Buttons = frantic/excited — and possibly unsuccessful — near-end-of movie dash by protagonist to stop love interest from leaving on ferry for THE OTHER SIDE OF THE HARBOUR/CHANNEL from which she would, of course, never be able to return. OR final sprint by Mel Gibson character in remake of Gallipoli (with Olympians in place of Oxygene) in which he frantically sprints back to the trenches in a failed attempt to stop the futile charge on the Turks. OR one of the less stressful moments in Run Lola Run.