Preheat oven to 350 degrees. In a large bowl, stir together the 2 cans of corn, corn muffin mix, sour cream, and melted butter. Pour into a greased 8 by 8 inch casserole dish. Bake for 45 minutes, or until golden brown. Remove from oven and top with cheddar cheese. Return to oven for 5-10 minutes, or until cheese is melted. Let stand at least 5 minutes and then serve warm.