Is my microwave still safe to use after accidentally heating metal in it?
My small kid used a metal bowl in a microwave oven and there was a spark. I immediately switched off the oven.
There was a burnt mark on the left side of the oven. Though the microwave oven switches on (Light is one), I am not sure if it actually works.
Will the microwave oven in general work even after such spark and burnt ?
The spark was a voltage jumping over a gap somewhere. This may occur again, but so long as the magnetron survives, you should be okay. The problem with sparks is they can leave a carbon trail deep inside which is conductive and may actually make the next spark occur at a slightly lower voltage. If this happens enough, you will eventually (or shortly) damage the unit and make it unusable.
I actually work as a product safety consultant and I can say, so long as you have an approved product (CSA, UL, ETL, or TUV) this sort of fault was actually tested. You should be a safe enough and not start a fire.