A melt sandwich (also known in Australia, New Zealand, and the United Kingdom as a toasted cheese sandwich or, toastie) is a type of sandwich consisting of bread, some sort of filling, and a layer of cheese, sometimes grated. The sandwich is then grilled or fried 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 would then be a tuna melt sandwich. Other popular choices are ham, roast beef, chicken, turkey, or a hamburger 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 were a staple of the traditional U.S. diner and were commonly found on menus as far back as the 1950s and possibly the 1940s.