Probably a bad door switch has caused the fuse to blow. Some makers of microwaves require that you change the door switch any time you blow the fuse. There are other factors that can blow the fuse including bad Capacitor, Diode etc. Do you have a meter to test any components?? If not start by changing the fuse and it that works then order a new door switch because it will happen again.

You need to discharge the capacitor first. take a insulated screwdriver and touch the capacitor prongs to the chassis of the micro. Usually a long screwdriver with plastic handle. Most caps discharge on there own but dont count on it!! touch the blade of the screwdriver to the push on fork of the cap and ground the screwdriver to the chassis. this will (or should) discharge the capacitor!! If you have any doubts at all dont screw with this cause it can kill you!! Looking back heres how this works. Take a Long insulated screwdriver. If there is room in your micro take the tip of the scredriver and touch and hold it onto the capacitor prongs and then while you keep touching the cap leads short the screwdriver to the chassis of the micro I. e just touch the screwdriver to metal of the chassis of micro while holding tip of screwdriver onto cap lead. WITH IT UNPLUGGED! Then resume testing components. Again if you are not comfortable doing this dont do it!!!!!!!!!!!!!

All these tests would probably require you to remove it from the wall. But i dont know your setup.