“Beyond the Circles of the World I will not pursue them,” said Morgoth. “For beyond the Circles of the World there is Nothing. But within them they shall not escape me, until they enter into Nothing.”
Even if the myths are lies, all the myths, we need them. We need stories. “If there were no God, it would have been necessary to invent him.” We need the Shaper, the bard in Grendel. To provide us with a model of how we should live. Even if we fall short--and we almost always do--we at least have a goal, and elevate ourselves in the attempt. Without the stories, we are all Grendel.
There's a ton of secondary literature on the web interpreting the various meanings of Grendel; I'm rather fond of this one: