Here's a great tip for keeping your metal cookie cutters from rusting.
First...remember....water is your nemesis.
Never let your metal cookie cutters soak in water.
All they really need is a quick wash and wipe.
As soon as you've cleaned the flour and cookie dough off of your cutters, give them a good wipe down with some MINERAL OIL.
You can either use a rag or a paper towel.
Just dump some mineral oil onto your cloth and wipe all the nooks and crannies and sides of your cookie cutters.
Mineral oil is considered a food grade oil. It is safe to use and it is safe to ingest.
Mineral oil is usually found in the health and beauty section of your local market or retail store and it's usually near the peroxide, rubbing alcohol and Epsom salt, or sometimes with stomach remedy medicines like Tums and Pepto.
After wiping the cookie cutters down, I like to store them in a ziplock bag, because the oil is an excellent magnet for dust...and I don't like dusty cookie cutters.