xpanam - sos pads are often my go-to, but have to be careful on what surfaces, but those inexpensive pads are basic tools to keep around your place.
Sandy - I agree about BKF being a little harsh-I made the mistake of using it on polished steel toaster.
Can't miss with Bon-Ami can: .."since 1886 - Hasn't Scratched Yet". Technique is everything, read label.
Favorite copper cleaner : Wrights (and they make a silver polish, for flatware that works well)
Favorite metal cleaner: Blue Magic Liquid Metal Polish (thought it does work on Chrome, Aluminum, Copper, Brass, God, Silver, Stainless Steel, Fibreglass...I have only used it on chrome and stainless...it restored a tea kettle that was so burnished and ruined by extended heat exposure...nothing else worked and this product is a paste that leaves zero scratches).
..will check out the Zud product and its relatives...thanks for posting