Prometheus was gifted knowledge from the goddess of wisdom, so he passed those skills onto mankind. He wasn't satisfied with what man had, so he gifted them fire.
This is a gift I bring to you mortals!
Prometheus got Athene to sneak him into the fire-chamber with the flaming chariot of the sun. He got a torch, lit it with the fiery chariot, and brought it back to the men. The men gazed in awe.
What have you done? You knew my command. Man was not to have the gift of fire.
I won't say I did obey your command. See how much happier they are, now that they have fire.
It soon came to Prometheus' attention that he needed to teach the men how to treat this new plaything so that they could remain in control.
Prometheus said," This is a gift that I bring to you from Olympus, mortals. It is called 'fire', and is stolen from the sun. But it is a dangerous gift and you must learn to treat it well."
Zeus was upset that Prometheus had disobeyed his commands and gave the mortals fire. Prometheus wasn't regretful though, he was glad that he made the mortals happier.
Prometheus was then forced to remain in torture for years and years. He was to bear the scorching heat of the sun by day, and the bitter cold at night. He was supposed to be chained to the rocks forever, but Zeus gave in and let a hero rescue him.