All other authorities or offices in the priesthood are appendages to the Melchizedek Priesthood (see Doctrine and Covenants 107:5), for it ?holds the right of presidency, and has power and authority over all the offices in the church in all ages of the world? (Doctrine and Covenants 107:8).
The most familiar example of the function of keys is in the performance of priesthood ordinances. An ordinance is a solemn act signifying the making of covenants and the promising of blessings. In the Church all ordinances are performed under the authorization of the priesthood leader who holds the keys for that ordinance. An ordinance is most commonly officiated by persons who have been ordained to an office in the priesthood acting under the direction of one who holds priesthood keys. For example, the holders of the various offices of the Aaronic Priesthood officiate in the ordinance of the sacrament under the keys and direction of the bishop, who holds the keys of the Aaronic Priesthood. The same principle applies to the priesthood ordinances in which women officiate in the temple. Though women do not hold an office in the priesthood, they perform sacred temple ordinances under the authorization of the president of the temple, who holds the keys for the ordinances of the temple. Another example of priesthood authority under the direction of one who holds the keys are the teachings of men and women called to teach the gospel, whether in classes in their home wards or in the mission field. Other examples are those who hold leadership positions in the ward and exercise priesthood authority in their leadership by reason of their callings and under the setting apart and direction of the priesthood leader who holds the keys in the ward or the stake. This is how the authority and power of the priesthood is exercised and enjoyed in The Church of Jesus Christ of Latter-day Saints.2
The principle that priesthood authority can be exercised only under the direction of the one who holds the keys for that function is fundamental in the Church, but this does not apply in the family. For example, a father presides and exercises the priesthood in his family by the authority of the priesthood he holds. He has no need to have the direction or approval of one holding priesthood keys in order to perform his various family functions. These include counseling the members of his family, holding family meetings, giving priesthood blessings to his wife and children, or giving healing blessings to family members or others.3 Church authorities teach family members but do not direct the exercise of priesthood authority in the family. The same principle applies when a father is absent and a mother is the family leader. She presides in her home and is instrumental in bringing the power and blessings of the priesthood into her family through her endowment and sealing in the temple. While she is not authorized to give the priesthood blessings that can be given only by a person holding a certain office in the priesthood, she can perform all of the other functions of family leadership. In doing so, she exercises the power of the priesthood for the benefit of the children over whom she presides in her position of leadership in the family.4 If fathers would magnify their priesthood in their own family, it would further the mission of the Church as much as anything else they might do. Fathers who hold the Melchizedek Priesthood should exercise their authority ?by persuasion, by long-suffering, by gentleness and meekness, and by love unfeigned? (Doctrine and Covenants 121:41). That high standard for the exercise of all priesthood authority is most important in the family. Holders of the priesthood should also keep the commandments so they will have the power of the priesthood to give blessings to their family members. They should cultivate loving family relationships so that family members will want to ask them for blessings. And parents should encourage more priesthood blessings in the family.5
In His sermon to multitudes recorded in the Bible and in the Book of Mormon, the Savior taught that mortal bodies can be full of light or full of darkness. We, of course, want to be filled with light, and our Savior taught us how we can make this happen. We should listen to messages about the truths of eternity. He used the example of our eye, through which we take light into our bodies. If our ?eye be single???in other words, if we are concentrating on receiving eternal light and understanding??He explained, ?thy whole body shall be full of light? (Matthew 6:22; 3 Nephi 13:22). But if our ?eye be evil???that is, if we look for evil and take that into our bodies??He warned, ?thy whole body shall be full of darkness? (verse 23). In other words, the light or darkness in our bodies depends on how we see??or receive??the eternal truths we are taught. We should follow the Savior?s invitation to seek and ask to understand the truths of eternity. He promises that our Father in Heaven is willing to teach everyone the truths they seek (see 3 Nephi 14:8). If we desire this and have our eye single to receive them, the Savior promises that the truths of eternity ?shall be opened? unto us (see 3 Nephi 14:7?8).
In contrast, Satan is anxious to confuse our thinking or to lead us astray on important matters like the operations of the priesthood of God. The Savior warned of such ?false prophets, who come to you in sheep?s clothing, but inwardly they are ravening wolves? (3 Nephi 14:15). He gave us this test to help us choose the truth from among different teachings that might confuse us: ?Ye shall know them by their fruits,? He taught (3 Nephi 14:16). ?A good tree cannot bring forth evil fruit, neither [can] a corrupt tree bring forth good fruit? (verse 18). Therefore, we should look to the results???the fruits???of principles that are taught and the persons who teach them. That is the best answer to many of the objections we hear against the Church and its doctrines and policies and leadership. Follow the test the Savior taught. Look to the fruits??the results.