This way-too-Hollywood spectacle is very loosely based on the legends of King Arthur. The creators made a story in which the “mages” are in war with humans resulting in a CGI-explosion in the opening scenes. This makes a thin bridge towards Arthur who is a commoner raised in a brothel.
The bad guy in the story is Vortigern (a very nice part of Jude Law) who tries to dominate the world. There is an alternative take on how the sword got stuck in the stone and of course Arthur is the one to get it out in order to thwart Vortigern’s plans.
Like I said, way-too-Hollywood with obligatory and unsuccessful drama, tons of over-the-top action, made-up elements and a fairly thin story.
The film may not be boring, but it has little to do with the Arthurian legends and all the extra elements did not really make an interesting story either.