Both the Platinum Card and Business Platinum Card by American Express received a metal makeover earlier, and current cardholders are able to trade their plastic versions for the new metal ones. You can make the switch either by calling the number on the rear of your card and asking for the metal replacement, or by logging into your online account and following these steps: (1) Click on Account Services, then (2) Order a Replacement Card for Damaged, Lost, or Stolen Cards, and (3) Request Metal Card.
Overall, there’s no additional value add with this update. Rather, the cards simply looks better, have a nice feel to them, and will likely be more durable to last the full 4-5 years before they hit their expiration dates.
Anyone applying for the cards from a new application will receive the metal card by default.
As a final note, if you have a lower-tier card (i.e. Green or Gold Card, either personal or business) and want the Platinum Card, be sure to submit a new application if you want to get the signup bonus (highly advisable). Simple calling in to upgrade to the Platinum Card will not allow you to receive the signup bonus (which is 60,000 points at the time of this writing and worth $600 at a minimum).
Pictured below: 1st image shows the plastic versions, 2nd image shows the new metal versions