Preheat the oven to 180°C.
In a bowl, mix flour, sugar, baking powder, and salt.
In another bowl, combine milk, egg, and melted butter.
Pour the wet ingredients into the dry ingredients and gently mix.
Divide the batter evenly into a muffin tin.
Bake in the preheated oven for 20 minutes.
Cool the muffins on a wire rack.