Energy (electricity) demand is rising dramatically around the globe, and coal is the cheapest (but dirtiest, unfortunately) way to produce it. It is also used in metals production.
It was down so long that it was overdue. It's about time it started moving back up, tho I wouldn't call this 'on fire'... more like a crawl up, depending on which one you're in. One thing that's usually nice about these types of stocks is, they move slowly, but steadily once they start moving. You don't see the rapid whipsaw of the momentum stocks.