Preheat the grill to medium-high heat, or around 400 degrees F.
Divide the ground beef into 6 equal portions. Using your hands, gently shape each portion into 1/3 pound patties that are slightly larger than the buns. (Pro tip: shape them so that the center of the patty is slightly thinner than the edges)
Season the patties with Montreal steak seasoning and seasoning salt on both sides.
Place patties onto the preheated grill, close the lid, and cook for approximately 4-5 minutes. Flip the burgers using a metal spatula, season, and continue cooking for an additional 4-5 minutes on the other side depending on how done you want them to be*.
Add a slice of your favorite cheese to each patty during the last minute of grilling. Close the lid to allow the cheese to melt.
Once the burgers are finished cooking, allow them to rest. Meanwhile, open each bun and brush both pieces with melted butter. Sprinkle with garlic salt then toast the hamburger buns cut-side down on the grill grates for about 1-2 minutes, or until they are lightly toasted.
To assemble the burgers, place each patty on a toasted bun and add your preferred toppings, such as lettuce, tomato, onion, pickles, and condiments. Enjoy!