Preheat waffle iron and read manufacturer's instructions. Melt butter in microwave. In a large bowl, combine flour, baking powder, salt and sugar. In another bowl, beat together milk and eggs. Whisk liquid mixture into dry ingredients until just combined. Stir in melted butter. Brush hot waffle iron with butter. Spoon about 1/2 cup of batter onto iron and close to cook. This first waffle will be the tester. Cook waffle until golden brown. Remove to plate and keep warm