<Soapbox warning>

I don't like the fact that regular steel wool leaves particles that rust (I fully realize that others don't see this as a problem); so if metal wool is indicated, then brass, or bronze. Most people don't realize that chrome plating has a deposit of chrome (the hardest stuff) that's only a few microns thick. When you've taken that away with abrasive, it's gone and it ain't coming back -- you're down to nickel then, much softer and can't compare to chromium for corrosion resistance. I prefer to keep things clean and corrosion-free in the first place, and I think that rust removal using chemical means such as oxalic acid is much better than using an abrasive. The less work the abrasive is, the more damage you've done to the chromium.

I can't tell you the number of times that I've seen architectural stainless steel wrecked because someone has used tools on it that they previously used on carbon steel. Stainless develops a chromium oxide coating passively, which is very thin, but when it's broken, and iron particles are ground in, it will never re-passivate, unless the entire finishing process is redone (and that's generally impossible outside a fabrication facility).

For polishing aluminum, virtually nothing will touch anodizing, or make it much better looking. And when dealing with non-anodized aluminum, using the finest abrasive possible is the best approach. The shinier and more reflective the finish (meaning that it isn't full of scratches), the more corrosion-resistant it will be.