I heated water in the microwave and it exploded inside. Water was pouring out even though the door was shut. I now know that I'm not supposed to heat water in the microwave. But I did and now after the water explosion, I'm not sure if I can use my microwave. Twelve hours after the explosion inside the microwave, I tried to warm up some vegetables and there were crazy noises and flashes of orange. Is this because the water hadn't dried out yet or is the microwave completely ruined?
Joe is essentially right. Bubbles form in a liquid at what are called nucleation sites - small irregularies in the container or in the liquid itself. If you look at the bottom of some beer glasses, there are little nodules (often in the shape of the brewer's logo) that nucleate bubbles of the CO2 that's dissolved in the beer. Much the same occurs with water - to nucleate bubbles of steam requires nucleation sites and, without them, the water can superheat to beyond it's normal boiling point of 100 C. When you then disturb the liquid, and so provide nucleation sites, a whole lump of it can turn to steam in an instant.
Permanent damage to the oven is possible but I'd leave it for a few days and then try again.