I recommend I Am the Cultivation Goldfinger. This novel is about cultivation. The protagonist, Su Ping, transmigrated to the world of cultivation and was chosen by the Goldfinger System. He transformed into the Goldfinger and helped the people of other worlds rise to power. He was an immortal cultivator with the thunder attribute as his main attribute, so he met the requirements of a system novel with a thunder attribute main character. I hope you like this fairy's recommendation. Muah ~π