Ford decided recently to build the body out of aluminum, the reason they claimed to have done this was to drop weight, boost fuel economy, and run more efficiently.

However, this causes major damage to the vehicle upon impact with anything. As well as the fact that they still do not have the best fuel economy, the bed gets destroyed when dropping weight back there, and the vehicle cannot tow near as much as a cummins, duramax, or a vortec. 

The photo to the right shows an aluminum body F-150 after a car crash.