D&C 84

In this revelation, the Lord explained that while in the wilderness -

"...Moses plainly taught to the children of Israel in the wilderness, and sought diligently to sanctify his people that they might behold the face of God;
24 But they hardened their hearts and could not endure his presence; therefore, the Lord in his wrath, for his anger was kindled against them, swore that they should not enter into his rest while in the wilderness, which rest is the fulness of his glory.
25 Therefore, he took Moses out of their midst, and the Holy Priesthood also..."  (Doctrine and Covenants | Section 84:23 - 25)

In other words, the Melchizedek priesthood and all associated higher ordinances and covenants were taken away which would mean the ordinances performed in Holy temples as well as the Gift of the Holy Ghost.  What remained was -

"...the lesser priesthood continued, which priesthood holdeth the key of the ministering of angels and the preparatory gospel;
27 Which gospel is the gospel of repentance and of baptism, and the remission of sins, and the law of carnal commandments, which the Lord in his wrath caused to continue with the house of Aaron among the children of Israel until John, whom God raised up, being filled with the Holy Ghost from his mother's womb."  (Doctrine and Covenants | Section 84:26 - 27)

Even thought these preparatory principles and ordinances are administered by the lesser priesthood. they are not insignificant.  Faith, repentance, and baptism is required for the remission of sins.  But with these saving principles and ordinance, was also the guidance of administering angels.

Of administering angels, Elder Dallin H. Oaks taught -

“The scriptures recite numerous instances where an angel appeared personally. Angelic appearances to Zacharias and Mary (see Luke 1) and to King Benjamin and Nephi, the grandson of Helaman (see Mosiah 3:2; 3 Ne. 7:17–18) are only a few examples. When I was young, I thought such personal appearances were the only meaning of the ministering of angels. As a young holder of the Aaronic Priesthood, I did not think I would see an angel, and I wondered what such appearances had to do with the Aaronic Priesthood.

“But the ministering of angels can also be unseen. Angelic messages can be delivered by a voice or merely by thoughts or feelings communicated to the mind. President John Taylor described ‘the action of the angels, or messengers of God, upon our minds, so that the heart can conceive . . . revelations from the eternal world’ (Gospel Kingdom, sel. G. Homer Durham [1987], 31.)

“Nephi described three manifestations of the ministering of angels when he reminded his rebellious brothers that (1) they had ‘seen an angel,’ (2) they had ‘heard his voice from time to time,’ and (3) also that an angel had ‘spoken unto [them] in a still small voice’ though they were ‘past feeling’ and ‘could not feel his words’ (1 Ne. 17:45). The scriptures contain many other statements that angels are sent to teach the gospel and bring men to Christ (see Hebrews. 1:14; Alma 39:19; Moroni. 7:25, 29, 31–32; D&C 20:35). Most angelic communications are felt or heard rather than seen.

“How does the Aaronic Priesthood hold the key to the ministering of angels? The answer is the same as for the Spirit of the Lord.

“In general, the blessings of spiritual companionship and communication are only available to those who are clean. As explained earlier, through the Aaronic Priesthood ordinances of baptism and the sacrament, we are cleansed of our sins and promised that if we keep our covenants we will always have His Spirit to be with us. I believe that promise not only refers to the Holy Ghost but also to the ministering of angels, for ‘angels speak by the power of the Holy Ghost; wherefore, they speak the words of Christ’ (2 Ne. 32:3.) So it is that those who hold the Aaronic Priesthood open the door for all Church members who worthily partake of the sacrament to enjoy the companionship of the Spirit of the Lord and the ministering of angels.” (“The Aaronic Priesthood and the Sacrament,” Ensign, November 1998, page 39.)

Administering angels then would be revelatory or guardian angels when we make and keep our sacred covenants.