A tuna melt sandwich is a classic comfort food featuring a hearty filling of tuna salad, usually made with canned tuna, mayonnaise, and seasonings, layered between slices of bread. The sandwich is topped with cheese—typically cheddar or Swiss—and then grilled or toasted until the bread is golden and the cheese is melted and bubbly. The result is a savory, warm, and creamy sandwich that's both satisfying and flavorful.