Melt is a grilled cheese sandwich with extra toppings to it like lettuce, bacon, ham, tomato, etc.
Grilled cheese has no toppings whatsoever. Just bread, shortening, and cheese. Some people are really strict about that.
I used American Cheese for my melt because I had no other cheese to use. I mashed the sardines into small bits and add it to the egg I was frying. Added bacon because bacon.