What does the dragon symbolize in excalibur?

The term dragon used in John Boormanâ??s film â??Excaliburâ?? is likely a product of books that were written long after â??Le Morte dâ??Arthurâ?? in pseudo histories such as Geoffrey of MontMartre's â??Kings of Britainâ??. However, in the classic legend, â??dragonâ?? likely represents a nature spirit.