Steel doesn't belong in an office microwave. Glass is the only real choice.

Glass is the only real option here, because stainless steel and microwaves simply don’t mix.

I don’t mean steel is “not as good” — I mean it can’t go in at all. Metal reflects microwaves instead of absorbing them, and thin edges (like the rim of a bento box) create sparking and arcing. That can damage the microwave’s magnetron, light up a container, and make you the person nobody talks to in the breakroom.

Glass, on the other hand, is basically perfect for this job. It heats evenly, doesn’t warp or stain, and won’t hold onto last night’s curry smell the way plastic does. Tempered or borosilicate glass handles the hot-to-cold shock of taking it straight from the fridge to the microwave without cracking.

Two small caveats: check the lid before you nuke it — plastic lids can be microwave-safe, but they need a vent — and avoid glass containers with metal rims, because that little metal ring will arc just as fast as a full steel box. Also, glass gets genuinely hot, so bring a hot pad or wrap the handles in a paper towel.

Save the steel bento for cold lunches and salads. The microwave is glass territory.