The monsters that Beowulf must fight in this Old English poem shape the poem's plot structure and appear to represent an inhuman or alien presence in society that must be exorcised for the safety of society. They are all outsiders, existing beyond the confines of human realms. Grendel and his mother's invasion of human society - they cause chaos in Heorot - forces Beowulf to kill the two beasts to restore order. As the poem progresses, it is clear that through the events of the poem and, more specifically, the way each event is described helps further the messages that are conveyed.