0000,,no heavier than that around firearms. The only thing I still use it for is occasionally with oil to remove some rust on blued surfaces.
Carding I do with a rotating brush, but used to do alot of it with steel wool. Messy and tiring way to do that. Get the oil out of the steel wool before you card if using it for that or on wood.
It'll scratch up nickel & other plated finishes except the hard chrome type.
I don't even like it on wood finish anymore. Those little shards of the wool imbedding in the wood. No matter how careful you are, you can find a couple stuck in there. Kind of ruins the day for you.
Scotch-Brite works great for me on metal and wood. I use the grey and maroon colored pads most. The white is almost too fine and doesn't cut at all. Green to really rough polish metal.
Keep these off of plated finished too,,they'll scratch them.
Keep pads used on stainless, brass(copper,silver,gold), and carbon steel separate. You'll drag one to the other with varying problems.
If you really want to polish, you go to polishing compounds or grit. Use dry or with water or oil depending on the job and gloss you want.
Stay away from buffers!