Pokémon the Movie 2000: The Power of One synopsis
Ash's adventure begins when a powerful storm beaches him and his friends on Shamouti Island just as the islanders are preparing to cast the hero role in their annual festival. They offer it to Ash. It sounds like fun, so he accepts. The festival enacts an ancient legend about three great and powerful Pokémon birds, Moltres, Zapdos and Articuno, who maintain nature's balance on the earth by ruling the elements of fire, lightning and ice.