Body side molding on a vehicle provides decoration and protection. Molding provides a contrast to otherwise large surfaces covered in paint. It also protects the vehicle from dents and dings that often occur in the parking lot.
As of 2015, many types of body side molding are made of polyvinyl chloride. This weather resistant plastic is flexible enough to absorb the force of another car door slamming into the side of the vehicle. Most manufacturers use rubberized glue to attach the trim to the car.
Older vehicles were often equipped with chrome molding attached to the car using metal clips. Because chrome coated metal was rust resistant, it served a similar purpose to the PVC molding manufacturers currently use.