I'm assuming the metal frame has an angle profile with holes for screws to go into the door frame at 90 degrees to each other. So some on the face of the frame and some on the inside of the frame. I'd mount the 3/4 screen molding an 1/8 or 1/4 in from the face of the door frame so that the holes in the metal angle line up with the center of the 3/4 molding. Pre-drill your holes or the molding will split. This will leave a small gap in the inside corner but that shouldn't make the metal frame loose or unsupported provided you get good connection from both the face and inside screws. You may want to buy screws for the inside holes that are a 1/4 inch longer so you still get good grip into the wood door frame.