Homemade Metal Polishes

Here are some recipes for homemade nontoxic metal polishes:

brass and copper polish: use lemon juice or tomato juice
chrome: use a cloth dipped in cider vinegar
silver: immerse the silver object in a bowl with aluminum foil and salt. Let sit a few minutes and then wipe the tarnish off.

Source: Debra Lynn Dadd Nontoxic, Natural, and Earthwise