Even the smallest scratch on your auto paint can cause problems. If left unattended, even a small paint chip can grow. It is especially bad if the metal becomes exposed and rust starts to form. This can lead to deterioration of the actual car's surface. You obviously want to avoid this at all costs. So, the easiest way to do this is to simply repair and reseal small paint chips before they become a problem. No matter how small a hole is, resealing it is a smart idea. Here is a basic guide to repairing paint chips.
Use Auto Body Filler
Auto body filler is essential for the job. It is sold at most home improvement or auto supply stores. The unique thing about auto body filler, compared to wood filler, is that it comes in two different parts. There is a large can of putty and then a small tube of hardener. You mix a small amount of hardener (consult the instructions) with the putty and mix them together before apply it to your car. The putty dries quite quickly once the hardener is applied, so you need to be prepared. You can use small mixing tray and a plastic putty knife to mix the two parts and then start to spread them onto the car.
Applying the filler is detailed work that takes a little bit of practice. You want to fill the hole and make sure the putty is pressed firmly into it so that there is no cavity. You will use the putty knife to try and spread the putty so it is relatively flat before it dries.
Sanding and Painting the Putty
You won't be able to perfectly sculpt the putty with the knife, so you will need to do some sanding once everything has dried. You need to invest in auto sandpaper. This is extremely fine paper and needs to be wet when you are using it. This is why it is often called wet sandpaper. Sand away the excess putty until it blends in with the auto surface and curves.
The final step is to cover up the putty spot with touch up paint. This is a simple task if you have factory replacement paint from the dealership. This is sold in small touch up cans, complete with a tiny brush for the touch up.
While the touch up paint might not look perfect, it is certainly preferable to a large rust spot or hole.