The door won't lift, or it lifts a few inches and stalls - that's usually a torsion spring that's already gone, not a weak opener. A loud bang from the garage, especially in cold weather, is often the spring itself letting go rather than something falling.
A door that looks crooked when it's halfway up, with one side higher than the other, points to one spring still holding on a double-spring setup while the other has failed - that's a job to stop using the door on, not push through. Slack in the cable, or a cable that's come off the drum, usually follows close behind a broken spring rather than causing it. If your door is original to a house built near 1985, the hardware age alone is reason enough to get it looked at before it fails on its own schedule. For more on how we cover Poolesville, see /near/poolesville/, or check /garage-door-spring-repair-germantown-md for how this same repair runs out of Germantown itself.