Active 'red' rust should be cleaned off gently and stabilized with a good preventative oil or wax. Search the forum here for 'rust' for more info.Opinions differ
The blue/black oxide form of iron oxide is 'patina' and should not be touched if possible. Brass or silver 'furniture' with oxide/patination is best just gently cleaned and oiled. Some like to polish silver, I don't unless it is my tableware. Some silver is just plated and polishing will eventually expose the copper/brass the silver used to be attached to.