What are the usual/common themes in an epic?
An epic is normally defined as a long narrative poem about the exploits of a national hero. Epics carry a culture's history, values, myths, legends, and traditions from one generation to the next. There are certainly many works of literature that are considered epics, such as Gilgamesh, Beowulf, The Illiad, The Odyssey and Sundiata. They all share the following characteristics:
1) They take the form of a long narrative poem about a quest, told in formal, elevated language.
2) They narrate the exploits of a larger-than-life hero who embodies the values of a particular culture
3) They begin with a statement of subject and theme, and, sometimes, a prayer to a deity
4) They deal with events on a large or "epic" scale
5) They use many of the conventions or oral storytelling, such as repetition, sound effects, figures of speech, and stock epithets
6) They often include gods and goddesses as characters
7) They mix myth, legend and history
Epics are well worth reading as they contain excellent adventures but also are valuable cultural gems that act as great teachers of a given society's values and core beliefs.
Many epics share themes having to do with the importance of hospitality and loyalty.
First, hospitality is absolutely necessary for the hero who must travel long distances from his home, among strangers. Without it, he has little chance for survival in strange and foreign lands. Civilized people provide hospitality not only because it is part of their moral code, but also because they would like to count on the hospitality of others should they ever need it.
Second, loyalty is as vital to the hero's happiness as hospitality is to his survival. Consider Odysseus's wife, Penelope, and son, Telemachus. Even after a twenty year absence, Penelope remains loyal to her husband, distinguishing herself as a good and true wife. Telemachus never gives up on the idea that his father will return to Ithaca, even risking personal danger to go in search of news of him. Those who betray the epic hero, on the other hand, are often punished thoroughly: consider the suitors who abuse Penelope's hospitality, attempt to force her to marry one of them, and threaten Odysseus's son.