A dome-shaped aluminum screw cover is adapted to be placed over the head of a self-tapping concrete screw that is used to fasten a metal structure to concrete on a house or building. A concave inner surface of the screw cover provides a space between the cover and the screw head for receiving a charge of silicone adhesive that bonds the cover to the metal structure and screw head, while also providing a watertight seal around the screw head that minimizes entry of moisture and corrosion of the screw. The screw cover is preferably of the same color as the metal structure so as to reduce its visibility while effectively concealing the unsightly screw head.