Who is St. Michael?

"The 'Iollach Mhicheil' -- the triumphal song of Michael -- is quite as much pagan as Christian. We have here, indeed, one of the most interesting and convincing instances of the transmutation of a personal symbol. St. Michael is on the surface a saint of extraordinary powers and the patron of the shores and the shore-folk; deeper, he is an angel, who is upon the sea what the angelical saint, St. George, is upon the land: deeper, he is a blending of the Roman Neptune and the Greek Poseidon: deeper, he is himself and ancient Celtic god: deeper, he is no other than Manannan, the god of ocean and all waters, in the Gaelic pantheon: as, once more, Manannan himself is dimly revealed to us as still more ancient, more primitive, and even as supreme in remote godhead, the Father of an immortal Clan"

-- Fiona Macleod, Iona