304 liner lunch box can't microwave. When 304 stainless steel is heated in the microwave oven, it will generate electric sparks and reflect microwaves, which is not only unfavorable for heating, but also damages the components of the microwave oven, impairs its performance and shortens its service life. When the microwave oven is heated, it will produce high temperature and high pressure, which will easily lead to the expansion of food and water in the lunch box, resulting in the deformation, explosion or food damage of the lunch box. So the 304 liner lunch box can't be microwave. As an electromagnetic wave, microwave also has wave-particle duality. The basic characteristics of microwave are penetration, reflection and absorption. For glass, plastic and porcelain, microwave can almost pass through without being absorbed. For water and food, it will absorb microwaves and heat itself. For metal things, it will reflect microwaves.