The lightest composite material available to make car body panels is carbon fiber. Carbon fiber is one-fifth the weight and stronger than steel.
As of 2015, carbon fiber is being tested to be used on luxury end cars, according to SAE International. The downside to using carbon fiber as a factory body panel is the cost of production. However, aftermarket carbon fiber hoods and panels can still be purchased and installed on a vehicle.
Carbon fiber must be properly reinforced with Kevlar in order to be structurally sound. If not, the material is easy to break. Unfortunately, when a carbon fiber panel is broken, the whole piece must be replaced, as it is not possible to fix the damaged area without producing the panel in its entirety.