While Grendel was full of themes, one of the main ones I noticed was Grendel's desire for community. Grendel is isolated from civilization because he is a monster. Grendel is an outsider, yet there are many instances in the book where he shows a need to be accepted. For example, he spends a lot of his time watching the townspeople. He thinks that humans and disgusting and absurd, but he would still like a chance to be a part of it. Instead, he is shunned for his existence. When he is finally aware that he cannot join the human race, he decides that the next best thing he can do is destroy it. He says, "So much for meaning as quality of life! I would kill her and teach them reality." (page 110).
The theme I have mentioned is definitely relevant to readers my own age. Teenagers are in a stage of their lives in which they search for acceptance. In the beginning of the book, Grendel was young, innocent, and just learning about the mysteries of life. Therefore, Grendel is a lot like a teenager himself. He is constantly learning, growing, and discovering new things. He notices the beauty in life along with the absurdities. He finds himself confused about the meaning of his life, and says, "My heart was light with Hrothgar's goodness, and leaden with grief at my own bloodthirsty ways." (page 48) Grendel yearns for a chance to be a part of a community, just as many readers my age probably do.
The most important word in Grendel would have to be "desire." Everyone desires something, and this is very evident in the book. First of all, Grendel desires acceptance into society. He does not understand why he is placed on such a different level when he thinks and speaks in the same way. He desires to know about life, and where he places in it. He also wishes his mother could speak. King Hrothgar desires to be a strong and powerful king. Even Grendel's mother seems to have a hidden desire to be able to communicate more fully.