Overall this show is fine for people who do not know or care about the glorious legend of King Arthur. There are so many moments which defer from the story many know and love of the King who united a land in upheaval. Now I won’t explain them all to spoil the five seasons of the show, just give a brief description.
It is an interesting premise to have the Prince Arthur growing up under the banishment of magic when we know that Arthur did not grow up in the Palace and that Merlin was known all around as the greatest sorcerer working openly in Arthur’s court. The creators of the show do bring in different aspects of the legend and those characters here and there while mostly making their own separate story which is fine without prior knowledge of King Arthur and the Knights of the Round Table.
However there are other problems with Merlin as an adventure series. Basically the same thing happens in every episode. The villain forms a new plan for the destruction of Camelot, it works for a minute, Merlin saves the day. Occasionally the villain actually takes Camelot and rules for about a week or two which is surprising, but a nice change from always failing. Also a fun moment for the role reversal of Arthur and Merlin sneaking into the castle to defeat the ruler of Camelot. However you can see the problem with Merlin as a successful show when magic is outlawed in the kingdom and Merlin is never able to do magic openly as the partnership we know of Merlin and King Arthur never comes to fruition in the show. Disappointing!
I have to say that it might be fine to watch for someone who enjoys fantasy without knowing about King Arthur, but that is an unlikely combination. I enjoy stories of King Arthur and am currently reading a book entitled A Connecticut Yankee in King Arthur’s Court which is a very fun story intertwining the legend and modernity in a most fascinating way. If you enjoy King Arthur I would suggest skipping this show and proceeding with the stories found in written form. Or enjoy some fantasy shows like Once Upon a Time or Charmed which don’t retell an epic legend in their own way.