From ArticleWorld

A bumper is an automotive component that is mounted on the front and on the rear of the vehicle. Bumpers are designed to withstand an impact in a collision, as well as allowing one vehicle to push another without damaging the body of the car.

Metal bumpers

The first bumpers were constructed of heavy steel usually in a single, wide band across the front and rear of the vehicle. Some of the earliest models of cars even had bumpers that were designed to act like a spring and absorb a portion of the impact. In the 1940’s and 1950’s chrome bumpers became popular. Chrome bumpers were designed and formed to match the shape of the car body, then plated with chrome and polished to a mirror like finish. Chrome bumpers are still popular on trucks, however they are rarely seen on newer model cars. As technology grew, bumpers began to be mounted to hydraulic pistons, this allowed the piston to absorb a portion of the impact, in the event of a collision.

Plastic bumpers

Bumpers on most modern cars are often referred to as plastic bumpers. This is because you can only see the plastic cover over the bumper. Under the plastic cover is a rigid metal bumper, often constructed of several pieces of steel that are folded and welded for exceptional strength. These bumpers are also mounted on hydraulic pistons that absorb a portion of the impact in the event of a collision. While these bumpers are superior in crash scenarios, they do not take well to pushing another vehicle. The plastic cover, while relatively easy to replace, is also relatively easy to damage. In hot, sunny regions the plastic may also become brittle over time, which can cause the cover to crack with even the smallest impact.