It’s all a question of frequency. Traditional sources of cooking heat use waves of infrared frequency to heat food, either directly as in grilling or broiling, or indirectly, where the fire heats the pot and the pot, by direct contact, heats the food. Infrared frequency (what we normally refer to as 'heat') cooks the food relatively gently, actually shaking it's molecules in a more or less agitated way, according to the degree of 'heat' applied.

Microwave ovens are different. Their relatively short, violent bursts of vibration in the longer microwave frequency band can only heat certain chemicals, principally the oxygen in water, but also the oxygen in amino acids, lipids and proteins. Whereas infrared waves induce a shaking motion, the alternating microwave electric current generated by the magnetron in every microwave oven forces the food molecules to 'rotate', (reverse polarity) at its microwave frequency (1-100 billion times a second).

The friction from this violent, thrashing motion tears at the food, vitamin and enzyme molecules, destroying, for instance, their cells' walls, while heating them savagely, [1] and changing their shape. "A basic hypothesis of natural medicine states that the introduction into the human body of molecules and energies to which it is not accustomed is much more likely to cause harm than good ... (In microwaved food) naturally occurring amino acids have been observed to undergo isomeric changes (ed.- changes in the arrangement of their atoms) as well as transformation into toxic forms”. [2]

No indirect heating via pots or plates is possible because hard materials resist rotation of their molecules. The pot or plate is only heated from direct contact with the heated microwaved food.