The term 'metal ring' can be broken down into two crossword solutions: washer (6 letters) and FERRULE (7 letters). A washer is a thin plate with a hole in the middle, usually made of metal, used to spread the load of a threaded fastener such as a bolt or nut. A FERRULE is a metal sleeve or band used to secure two parts together, such as a tube and fitting, or to reinforce a weakened part. Both washers and ferrules are commonly used in metal rings.