metal hitting metal while driving

Try raising the rear of the vehicle so that you can turn the rear tires by hand to see if the sound is found. If so, grasp the tire at the 9 and 3 o'clock positions and try to shake it to see if the hub bearing has play in it (play/wobble would indicate that the bearings are worn and need to be replaced) next remove the tire and check the brakes to see if they are badly worn or dragging. [second wheel bearing check] You can remove the the brake caliper and turn the wheel to see if the noise is present, if so the wheel bearing is the problem. Do this to both rear tire assemblies.