Most people have an opinion on what it should contain. Everybody knows it, instinctively. They are the ultimate. It's very rude to eat all the meat loaf. Even the main ingredient can vary.
Some recipes call for ground deer, elk, or moose meat.
Lentil and nut loaves can be as tasty and satisfying as meat. For the liquid element, important in keeping the loaf moist and preventing it from tasting like a giant, overcooked hamburger, substitute beer, ketchup and water or just plain ketchup, canned tomato or mushroom soup, applesauce, chicken stock, canned tomato sauce, or tomato or V-8 juice. Instead of soft bread crumbs, use oatmeal, dry cereal, slices of bread softened in the liquid, crushed crackers, stuffing mixes, bulgur, or cooked rice. Meat loaf can take a substantial amount of seasoning. Adding herbs and spices gives it character.