Ares first appeared on Xena in the Season 1 episode "The Reckoning." Suave, charming, witty, yet ruthless and amoral, he represented the seductive power of war and the dark side. He attempted to lure Xena to give up her new path of doing good and join him as his Warrior Queen. In "The Reckoning," he framed her for murdering three villagers in the hope that she would call on him for help when threatened with execution; in "Ties That Bind," he took the shape of her long-lost father Atrius and nearly tricked her into attacking a village. However, these plans were thwarted by Xena and Gabrielle.

In Season 2, Ares joined forces with Xena's now-dead archenemy Callisto and engineered a body switch so that Callisto's soul occupied Xena's body while Xena was trapped in Tartarus. He seemed to be grooming Callisto-in-Xena's body to be his new Warrior Queen, and had sex with her, but later turned away from her, realizing that she was too madly obsessed with revenge against Xena and too uncontrollable. Xena, who had persuaded Hades to release her, was able to send Callisto back to Tartarus.

In the next episode "Ten Little Warlords," the audience first saw a different side to Ares. After losing his godhood due to Sisyphus' trickery, he needed Xena's help to get it back; Xena reluctantly agreed to help him after realizing that the world needed a God of War and Ares was the best man for the job. As a mortal, Ares showed a new humanity and conscience, but after getting his godhood back he seemed to revert to his former cold-hearted self.

In Season 3 Ares' relationship with Xena grew more complicated; he was still trying to win her back to the fold (even using the Furies to drive her mad for that purpose in the season opener), but also tried to form an alliance with her to fight the evil god Dahak. Under threat from Dahak, Ares ended up briefly switching sides until Dahak was defeated by Xena. Ares also made an unusual appearance in the S3 musical episode "The Bitter Suite," where, as the "Emperor" in the fantasy land of Illusia, he personified the seductive appeal of the dark side. The tango Ares and Xena danced to Ares' song, "Come Melt into Me," also highlighted the erotic chemistry between the two.

Ares' character on Xena: Warrior Princess evolved dramatically in Season 5. A major part of the season's storyline involved the Twilight of the Gods and the rise of monotheistic religion. Determined to protect his own power and the rule of the Olympian gods, Ares killed Eli, a Jesus-like prophet who urged the people to abandon the old gods ("Seeds of Faith").

At the same time, however, Ares became less of a villain and more of a romantic interest. The sexual tension between Xena and Ares, and the suggestion that he was secretly in love with her, had been there all along. As early as Season 1, it was clear that he couldn't kill her; as a mortal in "Ten Little Warlords" he suggested that she could inspire him to change. His obsession with her was evident as well. (The S3 episode "The Furies" also suggested that he might be her father, but this scenario was later dropped.) In S5 the theme of Ares' love for Xena was brought out into the open. After the Fates prophesied that Xena's child Eve would bring about the end of the Olympian gods, Ares tried to declare his love for Xena, offering to protect her and her baby from the other gods and willingly become mortal if they could be together and have a child of their own. Xena rejected his offer, refusing to believe that his feelings could be sincere. Later, however, she used his help to defeat Athena.

When Xena and Gabrielle faked their deaths to escape the gods' persecution, Ares inadvertently thwarted their plans by burying them in an ice cave where they slept for 25 years. After mourning Xena for years, Ares unknowingly took Eve (now the Roman warrior Livia) as his protegée and lover. When Xena returned, he resumed his pursuit of her; enraged by her continuing rejection, he first encouraged Livia/Eve to kill her, and then joined the other Olympians in their effort to kill Eve. At the last minute, however, his love for Xena prevailed, and he gave up his godhood to heal the mortally wounded Gabrielle and Eve.

In "Coming Home," Xena risked her life to save the now-mortal Ares from the Furies. At the end of the episode, the two shared a tender kiss, and Xena told Ares, "You always got to me -- but you were bad for me, Ares; you still are." She also said that the chance of their ever being together was "one in a billion."

Later in the season Xena helped Ares again, hiding him from vengeful warlords on her family's farm ("Old Ares Had a Farm"). In "You Are There," she restored his godhood with a golden apple wrested from Odin, but refused his offer to become a goddess and rule by his side. In the next episode, "Path of Vengeance," Ares and Xena were once again adversaries as she foiled his plot to get the Amazons into a war with the Romans in order to gain more worshipers. However, they also seemed to share a new mutual understanding and acceptance.

The "uber" episodes of Xena (set in the future) suggest that at some point Ares was imprisoned in a tomb from which only a descendant of Xena's could free him ("The Xena Scrolls"), and that after getting out of the tomb, he continued to pursue a reincarnated Xena in the 20th Century ("Deja Vu All Over Again," "Soul Possession"). It is unclear whether these episodes were intended as actual part of the Xena storyline, or as jokes/parodies.

Much about the character of Ares and his relationship with Xena remained ambiguous, including whether he was at least partly redeemed by his love for Xena, or to what extent Xena reciprocated his feelings. Their relationship prior to the show's timeline is a mystery as well. The dialogue in "The Reckoning" strongly suggests that this is their first face-to-face meeting; subsequent episodes, however, establish that at some point in the past he trained her and may have been her lover as well. It is also implied that Ares gave Xena her signature weapon, the chakram.

The character of Ares on Hercules was quite different from his character on Xena. In the show's first season, prior to Ares' appearance on Xena, Ares appeared in non-human form as a skull in the moon or a fountain of blood (in one episode, he took the form of a slain warrior). He first appeared in the familiar form of Kevin Smith in the Season 3 "Hind trilogy," in which Hercules fell in love with Serena, a mysterious woman who sometimes became a golden hind and who was a protegée of Ares. Ares told Hercules that he would release Serena from her vow of service to him, and allow her and Hercules to marry, if Hercules gave up his superhuman strength. Later, Ares' underling, the god Strife, killed Serena and he and Ares attempted to frame Hercules for her murder. He was saved by the intervention of Xena and Zeus.

Ares' main goal on Hercules was to destroy his half-brother Hercules, both because Hercules constantly stood in his way by preventing wars and because he resented his father Zeus' preference for Hercules. Ares' schemes were invariably thwarted. In later episodes of Hercules, he changed from a dark villain to a more comical one.

In "Two Men and a Baby," it was revealed that Ares had sired a child with the now-mortal Goddess of Revenge, Nemesis. The child, Evander, was born with supernatural abilities (particularly telekinesis. Ares wanted to take the boy from Nemesis and raise him to be loyal to him, hoping to use him as a weapon against Hercules. However, Hercules and Iolaus managed to foil his plan and return the child to his mother. Later in that season, Ares teamed up with Callisto, now a goddess, to trap Hercules in a passageway between parallel world ("Armageddon Now"). Callisto (working with Dahak's daughter Hope) then turned on Ares, badly beat him in a hand-to-hand fight, and used a dagger dipped in the blood of a golden hind (lethal to gods, according to Xena/Hercules mythos) to kill Strife.

In "Reunions," Ares plotted with his mother Hera to kill Zeus.

In Season 5, Ares and Hercules briefly teamed up in "Revelations" to stop the Archangel Michael from destroying the world by unleashing the Apocalypse. In "Full Circle," Ares was back to plotting against Zeus, this time by releasing two of the Titans once imprisoned by the Gods, but Hercules and Iolaus stopped him again.

In the episodes "Stranger in a Strange World" and "Stranger and Stranger" the series introduced a parallel world in which Ares was the God of Love (wearing white and without facial hair), while Cupid was the God of War.

Ares also appeared in the two Hercules "ubers," "Yes, Virginia, There is a Hercules" (S4) and "For Those of You Just Joining Us" (S5). In those episodes, which were set in the present day and based on the premise that Kevin Sorbo was actually Hercules himself, Ares was still at war with his half-brother and was plotting to get Hercules: The Legendary Journeys off the air.