One can compare Grendel from the story about Beowulf with Goliath from David and Goliath in the Bible. Just as Grendel is against Beowulf, it is Goliath against David.
Grendel appears to be this monster that no one can beat, like Goliath does in the story of David and Goliath. Grendel is described as a vaguely human in shape, though much larger "... The Other, Warped into the shape of a man, moves beyond the pale Bigger Than any man, An Unnatural birth called Grendel by the country people into shapes days." (Pg. 95 lines 1351-1355), he has put fear into the people and no one seems to have the strength or courage to fight him "Grendel's hatred began, ... the monster relished his savage war. On the Danes,
keeping the bloody Feud. Alive, seeking no peace, Offering. No. truc, Accepting no settlement, no price. In gold or land, and Paying the living. For one crime only with another. No one waited for the repair from his plundering claws. That shadow of death hunted in the darknesss talked Hrothgar's warriors. " Although Grendel looks something like a man - HAVING two arms (or claws), two legs, and one head - he is much larger and Can Defeat Dozens of but at a time. He is protected from man's weapons by a magic charm. He Devour some of the dead on the spot and Carrie others back to his lair, the cave he shares with his mother beneath a mere in a dark fairy. The first night That Beowulf is with the Scyldings, Grendel stomps Up From The Swamp, bash open the mead-hall's door with a single tap, and Quickly Wolfs Down One of the geat inside. Just like Goliath is described as a Philistine warrior known for its gigantic proportions and exploits on the battlefield.
Although both Grendel and Goliath is described as two unbeatable characters, they have both a weakness. When David and Goliath met, Goliath mocked David greatly, and made fun of his choice of weapon, a stick and several stones. David, with faith in the Lord used sticks and stones to make a slingshot. With a properly aimed shot, David knocked Goliath unconscious and then used Goliath's own sword to behead him. Likewise is the meeting between Beowulf and Grendel. At a big party Beowulf is insulted by a relative of the king, and Beowulf replies that with proud words. When all guests are sleep Grendel shows up and attack them in their sleep. Beowulf goes into close fight with Grendel and rips his arms of in the battle, then Grendel returns to his home in a nearby lake.
And thats the similarity of those two stories together, one can say that the story of the battle between Beowulf and Grendel is just another way to tell the story of David and Goliath. It's all about the weak fighting the strong. David, the weak, finally wins with God's help over Goliath, the strong man. The message is that when evil and despair pile up, one should not let themselves be discouraged, but rely on God's power.