The bed of a pickup truck is probably one of the most abused parts of a truck. After all, it is designed to haul just about anything. There are a few options out there to protect the bed. Some companies make thick rubber mats to protect the bottom of the bed from damage. Depending on how you use your truck that might be all you need. Another very common option in many new trucks (less now than say a decade ago) is a plastic bedliner that rides on the inside of the bed and projects the bed from damage. The biggest downside to these bedliners is the damage they actually cause themselves. These liners rub the paint off the bed of the truck and basically help rust get a foothold.
Problem is it's disgusting inside. a foot of heavy sludge in the bottom and the walls and top are caked in a 3/8" thick layer of solidified grease. It looks and feels exactly like it was sprayed with plastic bedliner material or non-skid. It would take a month to chisel it all out and a needle scaler doesn't really affect it (too soft I guess).