Melt sandwich

A melt sandwich is a type of hot sandwich containing bread, cheese (sometimes grated) and some type of filling such as meat or vegetables. The sandwich is then heated until the cheese is melted. It may be served as an open face sandwich or a closed face one.
One common filling is tuna with mayonnaise; the result is a "tuna melt". Other popular choices are ham, roast beef, chicken, turkey, or a ground beef patty, which is known as a "patty melt". It is the filling that establishes the melt sandwich as a variation of the grilled cheese sandwich. Patty melts are a staple of the traditional U.S. diner and were commonly found on menus as early as the 1940s.