I recently had a simlar issue and the backing plate was involved. When making a sharp left turn at low speeds, I had a distinct metal tone sound coming form the right front.
My Mech thought it might be something simple, and so he suggested I take off the wheel and check it.
Well after I took off the wheel, I found the backing plate had been rubbing when the wheel was fully turned to the left.
I gave it a slight bend away from where it was rubbing, and the noise has not reappeared since.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.