Cheeseburgers can include variations in structure, ingredients and composition. As with other hamburgers, a cheeseburger may include toppings such as lettuce, tomato, onion, pickles, bacon, mayonnaise, ketchup, and mustard.In fast food restaurants, the cheese used in cheeseburgers is usually processed cheese. Other meltable cheeses may be used as alternatives. Common examples include cheddar, Swiss, mozzarella, blue cheese, and pepper jack.