Ares was born from Zeus and Hera was hated by both of them. None of the gods liked him, besides the goddess of beauty, Aphrodite. Ares was a man who had anger inside him because he always had thirst for fighting. Ares is the god of war who is excellent in fighting no matter where he is.
Anytime there was a battle, Ares would join just for the death and bloodshed. All he care was killing people and fighting which is why he is the god of war and violence.
When Ares was still a baby, two giants captured him and put him in a bronze jar. It wasn't until the giants' mother found out and told Hermes who rescued him.
Ares and his sister were always at odds. Ares is on the side of troy which is the enemy of Athena
Because him ans his sister were always odds, they started what is known as the "Trojan War". This war was fought between the Trojans and the Greeks.
The end of the battle resulted in Ares being defeated. Athena was more intelligent during battle while Ares just depended on his strength