Anybody here knows what product to put on outdoor metal ornaments to keep them from rusting?

I heard that there's a product you brush on any oudoor metal ornaments (like outdoor lamps, sconces, or hanging plaques made for outdoors,but rust anyway) to keep them from rusting. You brush the product on the item, let it dry, and it will not rust even if exposed to water. I just have no idea what the product name would be, or where to find it. :( help...