Like the rest of your house, a garage door requires occasional maintenance or repair. Because of its positioning by the driveway, the garage door can be subjected to bumps by a car or bike, or get tapped when backing a boat or trailer in the driveway, or can get struck by balls or a child's toys when children play in the driveway. It's nothing to get upset about, these things happen regularly enough for there to be common repair methods to fix the problem. On the other hand, garage doors can simply wear out with age over time and weathering.
Wear and Tear over Time
A garage door has a rough life comparative to the rest of your home's exterior simply because it is actively used several times every day. The springs or chain can break or more commonly the motor in the opener can burn out. Typically such failures require the part to be replaced rather than repaired and it takes an expert professional to understand what new parts to use based on the size and weight of your door. The door itself can become dirty or stained from weather and exhaust fumes, but that can often be fixed with a fresh coat of paint if the door is still in good shape. Of course, if you've always wanted a different style of door it might be a good time to consider a replacement if the old door such routine repair work.
Immediate damage is a bit different than wear and tear over time. Whether children are playing ball in the driveway or a guest's car accidentally taps the door, the damage needs to be repaired as quickly as possible. A broken window pane can be replaced fairly easily. A wooden or fiberglass door often needs to be replaced when damaged. A metal door may be able to be bent back into a working shape as a temporary fix, but it's going to put extra stress on the frame and opening system to leave it for long, it's going to be best in the future to go ahead and replace it as well.
Although you can buy a replacement door at a home improvement store, it's best to contact a professional contractor who specializes in garage doors. They will be able to install a new door quickly and efficiently using the proper parts which are compatible with each other so you don't have to worry about the door's functioning for years to come.