because they follow the western civilization
He is the god of all gods and god of the sky?
In the first book, The Lightning Thief, they are searching for Zeus's stolen lightning bolt.
west
The Olympians in the series are the Greek gods and goddesses of Mount Olympus. Easy to answer, really.
They represent themselves.
Sales men, minor gods, demigods, the muses, satyrs
Olympas...or the empire state building.
Zeus was important in the book "The Lightning Thief" because he was the ruler of the gods and the king of Olympus. When his lightning bolt was stolen, it caused a conflict among the gods and threatened the balance of power. Percy, the main character, had to retrieve the stolen bolt to prevent a war among the gods.
While The Lightning Thief is the first book of the Percy Jackson series, The Last Olympian is the fifth and last. In The Lightning Thief, Percy learns he is the son of Poseidon and is accused of Zeus's master bolt. In The Last Olympian, he defeats the evil god Kronos to bring peace to the gods at Mount Olympus.
Luke is a major part of the plot of the entire series while Ares only plays a minor part in The Lightning Thief and a part about as big in every other book in the series. If you look closely Ares was in the movie, just he didn't have an obvious role; he was at Olympus and could be seen if you looked very closely when Percy returned the bolt to Zeus. PLus Luke actually was The Lightning Thief in PJO: The Lightning Thief but Ares took it from Luke while Luke was on his way to Kronos (or Cronus, your choice.) The book states that gods were not allowed to steal from each other, and with Zeus being who he was, would you? The book also says that the gods often got heroes to do this kind of thing for them. That's why Luke stole the lightning bolt and not Ares, and why Percy had to get it back instead of Zeus or Poseidon.
The heroes, Percy, Annabeth, and Grover, discover that Luke was the Lightning Thief, and had framed them in front of the gods to make it look as if Percy was the one who stole the bolt.
The problem is resolved; the war between the gods is averted.