Originally Posted by Jeromee
It could be the backing plates on the rear brakes, they tend do to it with age. rust builds up behind them and pushes them out into the rotor.
I had the exact same problem 2 days ago, a metal on metal sound when I make right turns. The sound was coming from my front left side and i lifted my car on jack stands and rotated each wheel. The front left side was metal on metal when i turned the tire and i saw the backing plate of the front left was rubbing against the back side of the rotor, I just bent it out of the way and the problem was fixed.