Arod was a light horse of Rohan. It bore a Knight of Rohan in Éomer's éored that engaged the Orcs outside Fangorn. His rider was lost during the skirmish, but Arod himself survived and remained with the rest of the éored on their way back. In the Wold, Éomer gave him to Legolas.
Arod served his new rider faithfully, and for much of this time, Arod carried also Legolas's friend Gimli. At the Paths of the Dead Legolas spoke Elvish to calm the beast so that it would enter the Dark Door. Presumably he bore Legolas on his way throughout the War of the Ring and during the Battle of the Pelennor Fields.