Well, he’s not a single spirit. He’s three. The Holy Trinity. Father is Spirit, Son is Spirit, Holy Spirit is Spirit… Now the Son has flesh, so I guess both for the Son. The Father and Holy Spirit don’t have flesh at all though.
I know most Christian denominations teach God is Spirit, (Trinitarian and non-Trinitarian) except Mormons… in a way. I know Mormon theology pretty well, I’ve been studying them for a long time.
So, Mormons believe that the Father, Son, and Holy Spirit are God just not in the way we Catholics and most Christians who hold orthodoxy believe. They teach God is three persons, three beings, but he is one in purpose. That the three beings are united as one God because they all have the same purpose. They believe God the Father was once a man on another planet, or universe, depending on what Mormon you talk to. (Some Mormons may not know their church teaches that God the Father was once a man so that’s why some may deny it because of their ignorance.) They believe that he worshiped his own god, and when lived a good life following his god. They believe he was exalted by his own god, and got godhood. Because he was exalted he got his physical body back. They believe that somehow by his godhood he got the privilege to create another planet, (or universe) with life on it. They believe he and his wife, who also got exalted, had spirit children and that Jesus Christ was his first child. Then they believe that he became a man and got a body, kind of like we do. Only difference is we teach Jesus is the same being as the Father and Holy Spirit and that he is eternal. Then Mormons teach they don’t claim to know the origin of the Holy Spirit, just that he was a Spirit chosen by the Father to serve with him and his Son in the godhead and help humans out. They believe the Holy Spirit is pure spirit and has no body.