Here is an example of the repair process of panel damage to a car...
Step 1: Your car has sustained some damage. What does it have to go through to be back to its original state. Firstly, the damaged area will be thoroughly washed to remove dirt & grime.
Step 2: The panel beater will repair the damaged metal back to its original shape. He/she does this through a process of iterative beating and filing of the damaged area.
Step 3: After the beating process, some imperfections in the shape will still remain. These are removed using a bodyfiller. The area is then sanded to a smooth finish in readiness for the primer.
Step 4: After masking is put in place to protect the rest of the car, a rust preventing primer is applied, followed by a higher build undercoat to even out the paint work.