Consider classic pairings
The grilled cheese, like any sandwich, should always considered a neatly packaged meal. The flavors should be balanced, of course, but also stimulate and satiate the palate. So while white bread and American cheese may very well be considered the quintessential pairing, consider other classic combos as well. Cheddar, for instance, melts well and is a true knockout when paired with crisp bacon, tomato, and crusty sourdough bread. Topping a slice of a fresh baguette with gruyere and caramelized onions creates the sandwich iteration of French onion soup, and using an extra-drippy, ultra-stinky brie with honey, mustard, and apples—piled adventurously on raisin bread—is essentially like recreating the sandwich version of a baked brie. More adventurous cheese lovers might choose a stinky blue, which pairs well with pear and spicy arugula.