I heard an opinion that every man who has kept his first estate had the priesthood given to him before he came to earth. We know it was given to some in the pre-existence. For example in Teachings of the Prophet Joseph Smith, he said that Adam was given the priesthood prior to the creation of the earth (p 157). Joseph Fielding Smith said that “men chosen to positions of trust in the spirit world held the priesthood” (Conf Report Oct 1966, 84), and Bruce McConkie said that even Lucifer was once a holder of the Priesthood of God (New Witness for the Articles of Faith, 310). There are no comments I can find to really expound on this though. I am of the opinion that some may have been given the priesthood in the pre-existence, but not all. I am also of the opinion that no matter what position people held in premortal life, it is necessary for a physical conferring and ordination once this life is obtained. Afterall, we had no bodies before. Thoughts?
Priesthood is the authority to act for God; or, put another way, priesthood commissions divine governance. When a person is ordained to an office in the priesthood, there is a specific stewardship granted with set bounds. Just as a man could neither act nor direct the Lord’s work on the earth without the priesthood, so also was priesthood needed premortally to act for God and direct His work.
In the case of Adam, he was a part of the “presidency” over creation (Teachings of the Prophet Joseph Smith p 157). As such he needed authority to direct that work and would have thus held the priesthood. Little has been revealed about this particular priesthood because it is not used in mortality (you can use the example of a stake patriarch who has been released – he still holds the office of patriarch, but his authority to act in that office lies dormant). The priesthood held by Adam and other premortals was different from the priesthood they received on earth because the priesthood we are given in this life governs the affairs of this life. Premortal Adam could not be baptized, had no sickness to be healed of, could not marry, and had no dead to save vicariously. So he did not hold authority to perform those ordinances and direct that work until after he entered mortality and had a need for it.
Any aspects of the premortal life that did have a need for order would have been organized and governed by a premortal priesthood that would have been conferred at that time. Any aspects of mortal life that needs order is organized and governed by priesthood that is conferred in this life.