I love meatball subs! And they are so easy to make. I know you can buy frozen meatballs but I usually make my own by mixing 2 lbs. ground beef, an egg, some bread crumbs, worcestershire sauce, soy sauce, and garlic powder. Form into balls and cook in frying pan or oven. Pour your favorite spaghetti sauce into an oven safe dish and stick in oven to heat up. As meatballs finish cooking, transfer to dish. Let cook in oven until bubbly. Serve on sub bread and top with mozzarella or provolone.