if your micro wave oven is a new one (not years old) its probably a drain hole if its on the base for any fluid to drain off,all ovens of this type have holes in for ventilation etc
if the hole looks like a burn hole i:e: irregular in shape and maybe discoloured round the edge then i would say get a new one
Place a saucer under the microwave, beneath the hole to catch the microwaves � when the saucer is full (of microwaves), place it in the oven the next time you want to microwave food. Reduce the cooking time, allowing for the extra microwaves in the saucer.
I was just joining in with the nonsense replies you had received, prior to my post.
If you were to drill a hole in the enclosure/cover of your microwave oven (all the way to the cooking chamber) � providing that you ensure no body parts come within around 100mm of the hole, no damage to you will occur. It is very unlikely that enough microwave energy would leak out of the hole to heat food placed at the hole opening.
firstly everybody thinks that the gril lyou have in the door stops microwaves getting through. it doesn't. my science teacher had a microwave tester (can't rmemeber scientific name) and proved you still recieve microwaves up to 1 metre away from the machine.
plus theres no use using the power settings. with the tester my science teacher proved that the same amount are given off but if you put it on a low setting, they come on for 5 seconds then go off for 20 but because the lights still on and its making a noise you think itsstill microwaving.