Preheat your oven to 375°F (190°C) and line a muffin tin with paper liners or grease it lightly.
In a large mixing bowl, combine the flour, sugar, baking powder, and salt. Whisk together until well mixed.
In another bowl, whisk together the melted butter, milk, eggs, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and gently stir until just combined. Be careful not to overmix; a few lumps are okay.
Fold in the blueberries gently, ensuring they are evenly distributed throughout the batter.
Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.
Bake in the preheated oven for 18-22 minutes, or until a toothpick inserted into the center comes out clean.
Remove the muffins from the oven and let them cool in the tin for about 5 minutes before transferring them to a wire rack to cool completely.