I'm looking at a couple of low-cost Wifi modules that work with Arduinos. I was wondering what purpose does the metal cover on the board serve? (with the WiFi consortium markings). I'm guessing they cover the chip from physical damage but do they also act as an antenna? I've attached a few images I found off Sparkfun and Aliexpress. I've found it on almost all Wifi modules that are available on the market.