After the beef, the bun is unquestionably the most important element to a great hamburger. It can also be one of the most overthought and underappreciated decisions. Buns (or bread) are the delivery system and the only other ingredient necessary to call a burger a burger. A hamburger without a bun is a ground beefsteak, and a bun without a patty is just toast. Put the two together and you have a hamburger. Even without mustard, onions, pickles, or any of the myriad of other condiments available, it is still a burger.