The Thunder Helm

The Thunder Helm is a Side Quest in.

Overview
After Link regains control of the Divine Beast Vah Naboris from Calamity Ganon, the legendary Thunder Helm will rest on a pedestal beside Riju while she sits on her throne in the palace in Gerudo Town. When Link interacts with the Thunder Helm, Riju will offer to lend it to Link. However, she then says that Link must earn it by gaining the trust of her people. In exchange for resolving the Gerudo Town people's problems, Riju will lend Link the Thunder Helm. In order to satisfy Riju's terms, Link complete the four Side Quests in Gerudo Town that pertain to helping the people that live there. This includes "Tools of the Trade", "The Mystery Polluter", "Medicinal Molduga" and "The Search for Barta." Link does not need to complete "The Secret Club's Secret" in order to complete this quest.

Once Link has done all four Side Quests and returns to Riju, she tells Link that she has heard of his actions in delivering happiness to her people. Riju thanks Link, stating that he will always be a true friend of the Gerudo. As a reward, Riju keeps her promise and lends Link the Thunder Helm. Riju assures Link that he will be able to use the Thunder Helm to its fullest potential and unlock the power of Urbosa that lies within. While wearing the Thunder Helm, Link will not take any damage from lightning strikes.