I'm not sure if this is the same problem that everyone else is having but my '14 GT (stock brakes) was having a metal on metal noise also. It was more of a scraping sound that sounded like a front caliper hanging up causing the brake to drag. I took both wheels off and made sure that the sliders and calipers were lubed. The noise continued. It was most noticeable at around 20-30 mph. Eventually it started sounding like an air leak or hissing noise. I was going to take the wheels off again and look but for some reason stuck my hand through the wheel on the drivers side to see if I could feel any roughness on the inside of the rotor and found that the sheet metal dust shield was right up against the rotor! I did the same on the passenger side and there was a gap there. I went back to the drivers side and reached through the wheel and was able to bend the dust shield away from the rotor the way it should be. I haven't had a problem since. I bought the vehicle new with only a little over 100 miles on it so it must have been like that since it was delivered to the dealer.
Interesting, I'll have to try moving the dust shield away on mine, I know that it is REALLY close on some of the wheels. So close I can't even put my fingers between the shield and the rotor.