My bathtub drain is the type that you push on the stopper to close and then push again and it pops up to open. It is made by Delta. The stopper I am referring to is metal and is "fixed" in the drain. How do I remove this stopper mechanism to clean the drain. Thanks for any assistance you can give me.

The rubber seal has wilted or the crosshair under it is clogged. Put a screwdriver in it to hold the stem and then twist to unscrew the cap.. if that does not work, get a very long needlenose plier to hold the stem and unscrew it using the needlenose. If the clog is under the crosshair of the drain, make a small hook about 8 inches long with a hook about 1/2" long and put the hook in the hair and twist to catch the hair and pull up and out.