"This rare dragonfly only appears in the rain. Its wings direct electricity away from its body. Cook it with monster parts for an electricity-resistance elixir."
The Electric Darner (073 in the Hyrule Compendium) is a dragonfly and material found in Breath of the Wild. It can be cooked with monster parts to create an elixir that will provide electricity resistance or sold to shop-vendors for 2 rupees.
The best place to find an Electric Darner is just northeast of the Tabantha Bridge Stable. However, they will only appear when it is raining or during a thunderstorm. Alternatively, Link can purchase an electric darner from Beedle at the Riverside Stable for 10 rupees.