Ares (Ἄρης in Ancient Greek) is the God of war, bloodlust, and slaughter. In his worst aspect, he may also be considered to be the god of murder and unpredictable violence, yet he is also sometimes associated with courage and valor. He is the son of Zeus and Hera. He was given the name Mars by the Romans, who also associated him with the harvest, therefore making him much more prominent and respected in the Roman pantheon.
Ares typically dresses in a leather duster with a muscle shirt, a bulletproof vest (actually his shield in a modern version of itself), an iron padlock necklace, black jeans, and combat boots. He wears red tinted wraparound sunglasses to cover his eyes which are hollow sockets filled with flames. He is described as having black, oily crew cut hair, stands at 6' 7", with a bulked up body, and a handsome face with scarred cheeks. He rides a large, black Harley Davidson chopper motorcycle with a flame pattern paint job, a leather seat made from human skin, with shotgun holsters riveted to the motorcycles sides. This motorcycle is actually his war chariot in a modern version of itself. (Military motorcycles serve the same purpose as Ancient Greek war chariots.) He also has a hunting knife strapped to his thigh and an aluminum baseball bat (actually his spear in a modernized form) that can turn into various weapons, including a two handed broadsword and a shotgun.
Ares can change his appearance and turn into his Roman counterpart, Mars. As Mars, he becomes more disciplined, warlike (If possible), and militaristic. (again if possible). Also in the Roman myth, Mars was worshiped more than feared, even more so than Jupiter. He maybe also be less cruel than the Greek Ares.
Ares can best be described as prideful, violent, cruel, aloof, and rebellious; an easily angered bully who seems to care only about fighting, or as Rick Riordan put it: "He could pick a fight in an empty room". Because of this he isn't very well liked among the Gods. He was brainwashed into starting a fight among his family against his own will, and still thought it was amusing. As the god of war he has a degree of intelligence and is an expert in warfare. However, his temper and arrogance often lead to his own humiliation and defeat because these traits make him overconfident, leading him to underestimate others and make foolish mistakes. He will often focus more on brawn than brain when angered, making it easier for more clever opponents to overcome Ares' raw strength. He hates being called a coward and is willing to pick fights with people for no apparent reason. Due to being the god of war and bloodlust, Ares thinks that all problems are solved by hitting it, and encourages that violence, war, and rebellion are above everything else. Although he seem to show no one respect, he does have a soft spot for his daughters, who he loves, even though he can be strict to them.
Possesses the standard powers of a God in addition to having vast physical strength and the ability to control fire. As the god of war he is an expert in all areas of warfare. He owns a magic war chariot that can transform into different modes of travel including a motorcycle (his preferred form) and a German Panzer. One of his most notable possessions is his magical spear that can turn into various weapons. He also has the ability to invoke feelings of anger, passion and violence in others. In The Last Olympian it is shown that he give his blessing to notable warriors like Clarisse, giving them invulnerability when they show true courage and rightious wrath in the heat of battle.
He is Aphrodite's boyfriend, and has been for millenia. Her husband Hephaestus once caught them together in a golden net of his own design, and invited the gods to come and laugh at their affair. Hephaestus seems to enjoy inventing new ways to humiliate them, so Ares and Aphrodite pick the locations for their dates very carefully.
The children of this god are naturals with all weapons of war. They have also inherited their father's manipulation of fear. They can stir fright in those enemies to weak to fight it. These demigods often go into a fierce rage when in battle. While in this state weaker injuries are ignored, and their fighting abilities are much greater.