Through the authority of the Melchizedek Priesthood, Church leaders guide the Church and direct the preaching of the gospel throughout the world. In the ordinances of the Melchizedek Priesthood, "the power of godliness is manifest" (D&C 84:20). This greater priesthood was given to Adam and has been on the earth whenever the Lord has revealed His gospel. It was taken from the earth during the Great Apostasy, but it was restored in 1829, when the Apostles Peter, James, and John conferred it upon Joseph Smith and Oliver Cowdery.
"There are, in the church, two priesthoods, namely, the Melchizedek and Aaronic" (D&C 107:1). The Melchizedek Priesthood, which is "after the Order of the Son of God" (D&C 107:3), is the greater of these. It "holds the right of presidency, and has power and authority over all the offices in the church" (D&C 107:8). It also holds "the keys of all the spiritual blessings of the church" (D&C 107:18). It is named after a great high priest who lived during the time of the prophet Abraham (see D&C 107:2-4; see also Alma 13:14-19).
The offices of the Melchizedek Priesthood are Apostle, Seventy, patriarch, high priest, and elder. The President of the High Priesthood is the President of the Church (see D&C 107:64-66).
Men in the Church must be worthy Melchizedek Priesthood holders in order to receive the temple endowment and be sealed to their families for eternity. They have the authority to administer to the sick and give special blessings to family members and others. With the authorization of presiding priesthood leaders, they can bestow the gift of the Holy Ghost and ordain other worthy men to offices in the Aaronic and Melchizedek Priesthoods.
When a man receives the Melchizedek Priesthood, he enters into the oath and covenant of the priesthood. He covenants to be faithful, magnify his calling, "give diligent heed to the words of eternal life," and "live by every word that proceedeth forth from the mouth of God." Those who keep this covenant will be sanctified by the Spirit and receive "all that [the] Father hath." (See D&C 84:33-44.)