Don't microwave stainless steel lunch boxes.

Stainless steel lunch boxes are not safe to microwave, so move the food to glass or ceramic first.

Metal and microwaves don’t mix. Stainless steel reflects microwaves instead of absorbing them, which means your food stays cold while the box can throw sparks and arc against the oven walls. Worst case, you damage the magnetron — the part that actually generates the microwaves — and that’s an expensive repair over a lunch container.

Thin metal is the worst offender. Edges, handles, and corners act like little antennas and are the most likely spots to see sparks.

Yes, some newer stainless containers advertise “microwave-safe” metal. That only works with specific ovens that have special low-power modes, and even then it’s finicky. Your standard microwave at home? Not worth the gamble.

The plastic lid is usually fine, but the metal body isn’t. Just dump the food into a glass bowl. It takes ten seconds and costs nothing.

Future microwave you will thank you.