Never misabuse your oven for these experiments for more than 10-20 seconds. Below I will describe some nice things you can do with a microwave oven.
Most effects are quite spectactular.
For these experiments it's best to use an old type of microwave oven. Take an old CD or CD-R and put it in the oven, standing up. Put it against a glass cup or so. Don't use any metal as a holder. It will look like the image shown below.