In Beowulf contrast is an important structural element. The theme, characters and setting are all developed through the use of various contrasts, including good versus evil, light and dark, and youth versus age. .
The first time Grendel is mentioned, he is described as a descendent of Cain. Immediately, the reader knows that Grendel is evil, because Cain was the murderous son of Adam and Eve. "Conceived by a pair of those monsters born of Cain, murderous creatures banished by God."" (lines 20-21) Grendel began attacking Herot and eating men, a hideous act of evil. By contrast, as soon as Beowulf heard of the trouble that was facing Hrothgar, he immediately set sail to help the Danes. This act illustrates that Beowulf stands against evil. When Beowulf first reaches the island, he is asked for his lineage. Beowulf states that "My father was a famous soldier, known far and wide as a leader of men."" (line 174-176) This shows that Beowulf came from a good family, and it is in direct contrast to the evil roots of Grendel. Grendel comes from evil and becomes an evil monster, and Beowulf is from a brave and noble family and becomes a crusader for good. The theme of this poem, good versus evil, is clearly shown because of Beowulf-s attempts to rid the world of terrorizing monsters, like Grendel.
Just as the theme is developed through the contrast of the monsters' and Beowulf's basic natures, similarly the contrast of light and dark dominates the setting. .
Every time Beowulf and his men are mentioned, it is during the day or in a lighted place such as Herot. "Standing in the round-curled prow they could see sparkling hills, high and green jutting up over the shore, and rejoicing."" (lines 135-138) By contrast, darkness pervades the setting of the monsters. Grendel only attacks under the cover of night. "Then when darkness had dropped, Grendel went up to Herot."" (lines 30-31) Similarly, Grendel's mother lives deep under the watery depths, where hardly any light reaches.