Stainless steel CAN be heated in the microwave. This specifically designed stainless steel food storage container goes directly from the refrigerator into the microwave and back. There are no sparks, no hazards, just the convenience of heating your foods safely and quickly.
Both the Large and the Medium size Microboxes come with a 100% spill-proof platinum silicone cover and a steam-release vent. The Microbox is far better than heating your foods inside any plastic food containers where micro-plastics get released as the containers heat up. The Microbox is also extremely lightweight and practically unbreakable compared to glass containers.
The Large Microbox also comes with a salad strainer. Remember to pull the tab to release steam when heating.
I was concerned with putting anything metallic inside my microwave. I took a chance on this, put it in and heat on high for 5 seconds. I saw no sparks, so I did an additional minute. Now I am comfortable using this. I still can't figure it out though.
Personally I think this sort of product is ingenious. But it can also mislead some people. I called this company up and spoke to one of their engineers. Appararently there is a secret, and the secret is in the material and the shape. Their design allows stainless steel to be microwaved, but 99% of the metals out there cannot go into the microwave!