The recounting of the mythology of the Cyclops isn’t told in a single tale, but instead has been debated throughout history due to different versions told by Hesiod and Homer.
Hesiod described one group of Cyclops and the epic poet Homer described another; other accounts were written by the playwright Euripides, poet Theocritus and Roman epic poet Virgil.
In Hesiod’s Theogony, Zeus overthrew his own father (Cronus) and set the Cyclops free from the dark pit of Tartarus where they had been imprisoned by Cronus. Since they were metal workers and blacksmiths, they repaid Zeus with a thank you gift of thunder and lightning. The Cyclops also gifted the gods Poseidon with a trident, and Hades with the Helmet of Darkness.
The Gods waged war with the Titans (the elder Gods) for the better part of a decade. It was only thanks to the gifts skillfully created by the Cyclops that the Gods were able to overthrow the Titans.