Ms mia's personal Platinum card also has the Contactless feature, and also does not show the online option to order a metal card. Based on this sample of two I predict that you will receive another plastic card, with Contactless, and that the only way to switch to a metal card will be to call and opt out of Contactless. This seems to be further evidence that Contactless will not be available on the metal cards.
From a physics / engineering standpoint, I don't believe the metal cards cannot be contactless. The contactless cards have loops of copper wire around the outer portion of the card which go to a chip on the card. I would imagine that the metal card insert would block the RF energy / signal from the reader. Perhaps it is possible to design something that would work, but I'm having trouble thinking up a design that would be thin enough and sturdy enough to still be a metal card AND contactless.