when I was researching finishing wood for my first restore, some sites suggested that steel wool leaves material behind that will dull the natural color of wood. These sites suggested not using steel wool for finishing wood. I can't see an issue using it on metal and I in fact used some super fine wool to create a satin look on metal before.
Granted most research will show that there is not a direct correlation of wool and paper but I did find these pages when i was doing the reasearch....
SteelWool.biz _Grades & Uses
http://extension.usu.edu/files/publi...tion/HI_26.pdf
on the second page there you can compare the grit uses and the wool uses and try to line up the job you are working on.
hope that helps