We use aluminum foil to wrap a perishable item and preserve it, so a dream with this object in it relates to that which you may be keeping wrapped up inside your consciousness. This may or may not be of value to you; wrapping something precious will keep it preserved for a longer period of time, while keeping something under wraps may indicate that some idea or feeling may be better off if it were unwrapped. Aluminum foil is also used to increase heat around food for efficiency in the cooking process. In this way, it represents the enhancement of your ability to take in nurturance and sustenance and engage in self-care.
[1]