The aluminum trim on the front and rear bumpers of H-Bodies, with urethane bumper covers, is anodized. It can't be polished without removing the extremely hard anodizing either chemically or with a very aggressive machine polish. Over time, if left unprotected by wax, the anodizing will become stained, due to its porosity, and get a cloudy / water stained look.
An easy fix is to spray the trim with a gloss clear coat. The cloudy look / stains will disappear. Scratches however will still be visible.
The clear coat will need to be stripped and reapplied if it starts to yellow over time.
The other alternative is to strip the anodizing / polish the aluminum / then either re-anodize or clear coat. It is recommended that aluminum be anodized otherwise it will scratch very easily.
Paul