One type of ID badge that has retained the metal aesthetic of the old days is that of lawmen; the heavy metal look projects an air of authority you'll not get from a plastic rectangle. Let's have a look at some older cop badges:

These replicas of the badges commonly seen in America's Wild West are solid brass, except for the center badge, which is nickel-plated copper. (Source.)

Left and right, these police "pie-plate"-style badges from the late 1800s are made of Sterling silver with a 14K gold applique (!) and hand engraved. The Chief of Police (center) gets a decidedly fancier number, with presumably fake inset precious stones. (Source.)

These are the badges of today's New York Police Department, with the Sergeant in the middle and the Detective on the right. They retain the metal look, but are smaller, made of brass alloy, and are most certainly produced in a mold rather than hand engraved. (Source.)

Which is not to say there are no more fancy badges being made--purty custom badges can be ordered (for law enforcement only) online:

And last but not least, the City of Los Angeles' badge, below left, is a predictably glitzy affair. Click here if you're curious to see what those number call-outs represent, but also note that site erroneously states that LA had the nation's first oval badge in 1940. The 1st-issue Philadelphia Police badge, right, is from 1845.