Preheat the grill to 400°F. Clean the grill grates thoroughly with a non-wire brush or a piece of crumpled foil.
Add ground beef to a medium bowl. Add the garlic, onion, Worcestershire sauce, salt, and pepper. Mix briefly with a fork just enough to combine.
On a work surface, divide the mixture into six equally-sized balls. Using your hands, shape the balls into patties and create a slight indentation in the center of each (to compensate for expansion during cooking).
Grease the grill grates by wiping with oiled paper towels or spraying with nonstick cooking spray.
Place the burgers on the grill over direct heat and close the lid. Grill for 2 to 5 minutes depending on your desired doneness (see grill time chart). Open the lid and flip the burgers.
Grill for 2 to 5 minutes more. Check doneness by inserting an instant-read thermometer into the center of each patty: 125°F is rare, 135°F is medium rare, 145°F is medium, 155°F is medium-well and 165°F is well done.
Optional: Add the cheese to the burgers during the final minute of cooking to let it melt. Toast the buns by placing them on the grill away from the flame for one minute or less.
Place the buns on a serving platter facing up. Place the burgers onto the buns, add optional toppings and serve!