Scrap Metal is an item that is exclusive to the public test servers (external link), although it can be found in the 
Pusher, 
Loader and 
Cargo Hatch item selection menus in the actual game. Its sole purpose is to undergo testing by using it on a Recycler to obtain Metal. It can only be obtained from the cheat menu in the test servers, and cannot be obtained in the vanilla game.
16 scrap metal can drop 0-16 Metal.