OK, I actually do not know this directly, but remember it had to do with ions and hence did a fast search yielding the following:

"The composition of the bowl in which you beat egg whites can make a big difference. A copper bowl reacts chemically with egg whites to form fluffy, high-rise whites - it contains an ion which reacts with an egg white protein, specifically conalbumin, to form a more stable foam and helps the whites retain moisture.

The same result can be obtained using stainless steel or glass bowls with the addition of cream of tartar. However, I don't use a glass bowl because I have found that when using it, its naturally slick surface doesn't give much traction for the egg whites to climb the bowl.

Avoid plastic or wooden bowls because of their naturally porous surface which attracts grease because of its porous surface; grease or fat deflates egg whites. Never use aluminum which reacts with the egg whites causing them to turn slightly gray."

I've always wondered this too! One reason why people use metal containers to whip cream is that metal will stay cold when chilled, and it is important when making whipped cream that you beat the cream when it is cold and keep it cold while beating it. Since the beating process generates heat, whipping the cream in a cold metal bowl can help counteract this buildup of heat.

What happens when you whip heavy cream with lots of fat in it The fat forms a matrix that traps air (tiny drops of fat disperse evenly and stick together). This fat matrix falls apart when warm.(Egg whites whip up the same way not because of fat but protein, so they remain somewhat solid at room temperature. Copper bowls help the process of beating egg whites, but this is a different story.) Cool Whip isn't real whipped cream, so itdoesn't melt as easily.

You could probably mix whipped cream in a glass or plastic bowl if you did so in a cold room with cold beaters and cold cream. Adding a little gelatin to stabilize the whipped cream (make it more firm) might also help.

I was not able to find out anything about whip cream and metal bowls. I do know that the temperature at which you whip the cream is very important. Some recipes call for refrigerating the cream, bowl, and beaters before starting the whipping. The reason for this is to make sure the fat globules in the cream are as stiff as possible - they hold a better foam that way.

I know that copper bowls are better than any other kind for whipping egg white because the copper ions form a complex with the egg white proteins and help make them more stable. Perhaps there is something similar that does on with whipping cream and iron or zinc ions in a stainless steel bowl.
Happy Cooking.