Clay bars have the ability to grab the tiniest of debris and hold onto it as it glides across the paint. Detailing clay bars are not abrasive and will not harm the paint surface with the exception of cleaning it. Anything that protrudes above the top coat surface will be grabbed by the clay bar and pulled out. The clay lubricant will prevent this debris from scratching the vehicle. Once clayed, the paint will feel remarkably smooth and have the shine that comes with perfectly clean paint.
Clay pulls out things you can’t see, like industrial fallout, rail dust, and brake dust. Though they are not visible, they feel bumpy or gritty and they may cause patches of paint to appear dull, even after waxing. Even worse, as these contaminants oxidize, they create rust spots within the paint. Once this happens, the oxidation is considerably harder to remove and will most likely take a good bit of paint with it.
Likewise, chrome and coated metal and glass are subject to the same environmental pollutants as the paint. We use clay to clean these surfaces, too. It will not scratch metal or glass!