Preheat the oven to 350°F (175°C) and grease a loaf pan.
In a large mixing bowl, whisk together the melted butter, sugar, eggs, and milk until smooth.
Add the flour and baking powder, mixing gently until just combined. Do not overmix.
Carefully fold in the fresh blueberries, distributing them evenly throughout the batter.
Pour the batter into the prepared loaf pan and spread it evenly.
Bake for 50 minutes, or until a toothpick inserted into the center comes out clean.
Allow the loaf to cool in the pan for 10–15 minutes, then transfer it to a wire rack to cool completely before slicing and serving.