What are some points that can be made in an essay on the legend of King Arthur and the significance of the Sword in the Stone?
I had to edit down the original question. I also think that in the construction of any essay and points that can be made, you might have to make reference to the original assignment. That should be your primary guide in developing your essay.
With this in mind, I think that a really good essay topic could be to examine the elements of the heroic archetype that are embedded in the King Arthur legend. Using the standard archetype of the hero and the notions that are a part of the heroic quest, it is really interesting to note where these are in the Arthurian legend. The idea of the child being isolated from society is seen in King Arthur needing to be raised away from the social order. At the same time, the use of an external adviser to raise the child is evident in how Merlin takes over the rearing duties of the young king.
Another example of the heroic archetype evident in the King Arthur legend is a struggle for power. There is a legitimate question after King Arthur's father dies as to who will take over and it is in this void that King Arthur asserts himself. The sword in the stone and its extraction help to demonstrate other aspects of the heroic archetype. The hero being able to do something that few others, if anyone can do, is seen in the young Arthur being able to pull the sword out of the stone. Excalibur, as a weapon, becomes the sword of choice for King Arthur, reflective of the specific type of weapons that benefit the hero.
The immediate awe with which others view King Arthur after the Sword in the Stone moment is another element in which one can see the heroic archetype being displayed. The hero is a distinct part of society due to their feats. I think that these are elements of the King Arthur legend that help to establish the heroic archetype or pattern in King Arthur that might make for a strong paper being developed.