Sandwiches can contain anything, just like a taco can. Everyone knows that.

But when a sandwich contains cheese along with other additional internal ingredients, the act of grilling it is metamorphosical. In this irreversible process, it ceases to be a sandwich and becomes a melt.

So while a tomato and cheese sandwich can be an amazing and delicious thing, a grilled tomato and cheese sandwich is impossible.

To say that it is any other way would be like saying that a caterpillar and a butterfly are the same thing.