Butter one side of each slice of bread. Place 4 slices, buttered side down on a hot skillet or grill. Add 4 slices American cheese (or more!), and top each with 1/4 of the bacon. Place remaining slices of bread on each, buttered side on outside. Cook 2-3 minutes, then flip and cook another 2-3 minutes, until toasty and warmed through.