The name of Perkūnas has multiple variations across the Baltic- and Finnish-speaking regions. In Lithuanian, his name is Perkūnas, while in Latvian, he is Pērkons. In Yotvingian he is known as Parkuns, whereas Perkele is his Finnish name. His name in Old Prussian is Perkūns.
His name is also linguistically related to the Slavic Perun, Sanskrit Parjanya, Finnish Perkele and Greek Keraunos, all of which relate his Perkūnas' role as a rain/sky/thunder god. Additionally, his association with oak trees is shared with Zeus.
Perkūnas was a warrior-god of the sky, who was originally married to Saulė, the solar goddess, who cheated on his with Mėnulis, the moon god. In anger, Perkūnas strikes at Mėnulis, causing the other to spilt in half. The moon god regenerates, but does still not learn from this and continues to have affairs with other deities, such as Aušrinė, the morning star, and thus Perkūnas continues to strike the moon every month explaining the lunar cycle.
In some other myths he is married to the goddess Lauma, who is kidnapped by Velnias, a Baltic demon, which causes a rivalry between the two, though his most common consort is the Earth-goddess Žemyna. He is also said to have four sons, who are the cardinal directions of east, west, south and north.
Perkūnas has also a rivalry with the before mentioned Velnias, who is either a demon or god of the underworld, which either stems from the kidnapping of Lauma or the theft of cattle. The thunder-god is often described in chasing his enemy, who hides among the trees and the rocks of the Earth, in a fiery chariot or riding a fiery horse. This rivalry always ends in a battle in the form of a thunderstorm.
He also appeared in the story of Jūratė and Kastytis, in which he was angered about the news that the beautiful goddess of the sea, Jūratė, had taken mortal lover named Kastytis. He decided to strike Jūratė's mansion with a thunder-bolt, which shattered it millions of pieces and killed Kastysis. Jurate herself was chained by the thunder-god to the bottom of the sea, where she started weeping, her tears becoming the pieces of amber that are still discovered at shores of the Baltic Sea to this very day.
Perkūnas in his chariot would be identified with the constellation of Ursa Major.