Cooked food should not be kept in cast iron utensils overnight as this could cause a metallic taste to develop in the food. In general, you want to keep your cast-iron utensil as dry as possible to protect the seasoning and avoid rusting. The seasoning will degrade because of the acids in the food that is left in the cast iron utensil. It's crucial to keep cast iron utensils dry and avoid the possibility of letting anything stick to them.