Some of it is plastic, some is stainless around the windows, but most is metal. Once the chrome is stained or etched there is no fixing it besides replacing, however. You can only keep it polished and waxed often for protection. The stainless around the windows seems to hold up well, but the other spots not so much. The road treatment used in CT in winter is notorious for staining chrome, and the stain goes deep.
2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6, 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac