Preheat oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners.
In a medium bowl, whisk together flour, sugar, baking powder, and salt.
In a large bowl, whisk together melted butter, milk, eggs, and vanilla extract.
Add the dry ingredients to the wet ingredients and stir until just combined. Do not overmix.
Gently fold in the blueberries.
Divide the batter evenly among the muffin cups.
Bake for 20 minutes or until the muffins are golden brown and a toothpick inserted into the center of a muffin comes out clean.