Putting a candle in a microwave is fun because sometimes you can see a plasma. 
 HOWEVER SAFETY IS VERY IMPORTANT! 
The microwave oven, or parts of it, like the paint on the walls, can catch on fiire (see picture below).  The microwave can be ruined, and you can start a f ire in the room.  EVERY TIME I DO THIS I HAVE A FIRE EXTINGUISHER AND SAFETY GOGGLES! I also use other safety equipment and make sure I will not endanger other people.    Reading this web site DOES NOT qualify you to create microwave plasmas.  Do not do so unless you have the permission of the microwave's owner and are taking proper safety precautions.  Until then, pictures and YouTube are invaluable ways to see candles in microwaves.