Aluminum Foil Sheets can help keep things warm through a process called radiation. When you wrap an object in aluminum foil, it reflects back the heat that the object emits, effectively trapping it inside. This works similarly to how a mirror reflects light. So, when you wrap a warm sandwich or leftovers in aluminum foil, it helps to retain the heat within the food, keeping it warm for a longer period of time. Additionally, aluminum foil also acts as a barrier to prevent heat loss through convection and conduction, further aiding in insulation.