Does my Water-Heater stand need to be metal or fire rated drywall?
There certainly are codes written for how to install appliances, especially gas ones. There is also specific rules for how to install drinking water appliances, so in the course of a Water Heater, you have both.

Here is an example (google) for Las Vegas Nevada. That is just an example. You should check your local county/town ordinance and verify their rules. Also, check your water heater model # and read the manufacturers guidelines.

I'm not too sure why you would use drywall for a stand? Is there a different portion of the question you meant to ask? You would not want to frame a stand out of Drywall. Conversely, Making a stand out of plywood works, but only if it meets code and is well built to hold the load of the water + tank weight + some % buffer (say, 25% SWAG).

Anyways, here is a really good discussion on this very topic here: How high to raise water heater above floor?

Oh, I almost forgot - based on code &amp; manufacturer, you may not have to raise it at all, but the cinder block approach is pretty foolproof.