Don't Microwave the Lunch Box

No — you shouldn’t microwave food directly in a lunch box with a metal interior or metal trim.

Metal and microwaves don’t mix. Microwaves heat food by passing through it, but metal reflects them. If the interior is metal, your lunch is basically sitting inside a shield — the food won’t heat properly, and the metal can spark and arc, especially if it’s thin or has edges.

Metal trim is the same risk, just smaller. Even a decorative strip can throw sparks if it’s close to the oven walls or has a sharp point. Not worth testing.

Just move the food to a microwave-safe bowl or plate. That takes thirty seconds and avoids a potential fire.