mine does that too, but compared to all the issues I've had, it's so minor that I can't get worked up about it. The metal should be attached to the thin plastic trim so I assume that you could probably glue it back somehow? I push mine down and it stays in place for a day or so, after which it pops up again. It's mainly visible from the sides.
If it bothers you, take it to apple. They'll probably just swap the top palmrests for you.