Zeus was the Greek god of the sky but also the supreme ruler of Mount Olympus, which domain included: all of the Olympian pantheon of gods as well as all of the earth, a mighty position indeed.
Zeus (not surprisingly) had an unorthodox childhood. At the time of Zeus’s conception Cronus, Zeus’s father, had been eating whole all the children his wife, Rhea, had born him. Not because they looked oh so scrumptious, but because of a prophecy that Cronus would be overthrown by one of his children. So simple solution: just eat your children.
However when Rhea had born Zeus she knew she couldn’t hand him over to Cronus to be devoured, so instead of handing Cronus Zeus to eat she took some clothes and wrapped a rock and gave that to Cronus (Cronus must have been as smart as one to actually fall for that). After she was safe she sent little Zeus to earth to be raised by nymphs and the divine goat Amalthea. Amalthea was also important later on because upon her death Zeus was moved to sadness and used her horn as the cornucopia and eventually used her golden fleece as the impregnable aegis. 
Once he grew to be a young man Rhea sought him once more and brought him back to the gods, where Cronus employed him as the royal cupbearer of the Gods, not even suspecting that it was his son. Eventually Zeus was given a special wine, given to him by Metis, the Titan Goddess of Wisdom, to bear to Cronus. Upon swallowing it he vomited all of the previous children he had swallowed: Hestia, Demeter, Hera, Hades, and Poseidon. 
Upon the regurgitation of his brothers and sisters he they were understandably pissed for having been digested for the last couple decades and so Zeus was able to band them together to wrest power away from Cronus and the Titans in a long bloody war that followed. They intended to give Cronus his just desserts (desserts that didn’t involve them).
The first thing they needed was some weaponry. So their first move was to travel into Tartarus together and free the Cyclopes who had been imprisoned there by Cronus. Upon freeing them they were so full of gratitude that they forged three excellent weapons. To Hades they gave him a magical helm which rendered him invisible while he wore it, a trident to Poseidon, and thunderbolts to Zeus.