Homer's The Iliad is one of the most famous examples of Classic Greek poetry. 

Epic poetry is characterized by lengthy narrative and themes of heroism or a journey. Many other genres have been influenced by and developed from epic poetry- the epic novel, film, or television program similarly draw from tales of long, heroic journeys.

The Iliad is set during the Trojan War and describes the final weeks of the war and the events surrounding characters like Achilles, Agamemnon, Patroclus, and Odysseus. In a companion piece to The Iliad, called The Odyssey, Odysseus must make the long journey home from war. This, too, is an example of epic poetry. The Iliad is characteristic of epic poetry first because it is quite long, and also because it tells of tremendous battles on Earth (between humans) and how the Gods (on Olympus) interfere. This transcendence of mundane events, where supernatural and earthly beings interact, is quite common in epic poetry.