Hades was lonely, and wanted a wife. He spied Persephone one day, in the fields with her mother Demeter, and decided he would have her, admiring her (in other cases, Hades was riding his chariot over the Earth. When Eros saw him, he shot a golden arrow into Hades. Persephone was the first one he saw, resulting in 'love at first sight'). He soon fell in love with her, and plotted on how he would get her. After obtaining the permission of Zeus he decided to kidnap her. Persephone was innocently picking flowers with some Nymphs in a field in Enna when Hades came to abduct her, bursting through a cleft in the Earth. Later, the Nymphs were changed by Demeter into the Sirens for not having interfered. Life came to a standstill as the devastated Demeter, goddess of the Harvest, searched everywhere for her lost daughter. Hecate, Goddess of magic, eventually told Demeter she had heard Persephone screaming that she was being kidnapped. She then stopped working the Earth, and the land didn't flourish.
Hades was determined to make Persephone love him, and tried in many ways. She hated him at first, for snatching her away from her mother, but she soon revealed that her mother wasn't around, as she had never been away from her before. He very much wanted her love and tried to buy it with many gifts at first, but then took to spending all of his day with her, trying to make her happy.
Finally, Zeus, pressed by the cries of the hungry people and by the other deities who also heard their anguish, forced Hades to return Persephone. However, it was a rule of the Fates that whoever consumed food or drink in the Underworld was doomed to spend an eternity there. Before Persephone was released to Hermes, who had been sent to retrieve her, Hades convinced Persephone to eat six pomegranate seeds, knowing they would eternally connect her to return to the Underworld and force her to return for six months each year. This explains why we have winter. Some versions of the myth have Persephone eventually fall in love with her new husband in return, and other at least say that she respected him and her new powers as Queen of the Underworld.
When Demeter and her daughter were united, the Earth flourished with vegetation and colour, but for six months each year when Persephone returned to the Underworld, Demeter mourned and the earth once again became a barren realm, thus creating seasons.
In the Underworld, Hades has dominion over the dead and demons. He is one of the Big Three rivalled only by his brothers Zeus and Poseidon. He naturally wields all demonic power and is able to use it for many effects including throwing black fireballs, (which turn any thing they touch into a liquid), summoning endless waves of the dead to fight for him, shadow manipulation (umbrakineses, etc. Hades' son, Nico di Angelo, is able to use many different underworld powers, Hades has the same powers, but extremely more advanced). Many times he is shown using dark energy as a shield or an attack. He is immune to electricity, being geokinetic and the fact he survive the lighting strike at that killed Maria De Angelo and incinerated an entire city block. He is able to manipulate Stygian iron, like his son Nico. Has all the natural abilities shared by all gods, immortality, superhuman strength, speed, senses, durability, agility, healing, endurance, teleportation/extremely rapid flight, transformation and invulnerability (except to Celestial Bronze, Stygion Iron, Silver, and Imperial Gold).