What happened when Percy took the lightning bolt to Zeus?

The bolt willingly flew into Zeus' hand.

Zeus opened his palm. The lightning bolt flew into it. As he closed his fist, the metallic points flared with electricity, until he was holding what looked more like the classic thunderbolt, a twenty- foot javelin of arcing, hissing energy that made the hairs on my scalp rise.

Zeus spares Percy's life.

“To show you my thanks, I shall spare your life. I do not trust you, Perseus Jackson. I do not like what your arrival means for the future of Olympus. But for the sake of peace in the family, I shall let you live.”