The High Priest
"As a result of the failure of the Israelites to observe the gospel law administered by Moses under the authority of the Melchizedek Priesthood, the Lord gave an additional law of performances and ordinances and 'confirmed a priesthood also upon Aaron and his seed, throughout all their generations' (D&C 84: 18) to administer it. This priesthood was of lesser power and authority than the priesthood of Melchizedek, and was used to administer the outward ordinances, particularly as characterized by the ceremonies of the law of Moses. The terms Aaronic and Levitical are sometimes used synonymously (D&C 107: 1, 6, 10), although there are some specific differences in the offices existing within the Levitical Priesthood. For example, the lesser priesthood was conferred only upon men of the tribe of Levi. However, within the tribe, only Aaron and his sons could hold the office of priest. And, still further, from the firstborn of Aaron’s sons (after Aaron) was selected the high priest (or president of the priests). Thus Aaron and his sons after him had greater offices in the Levitical Priesthood than did the other Levites."
-"Aaronic Priesthood" LDS Bible Dictionary, LDS edition of the Holy Bible p.599
This afternoon I read an interesting blog post on http://ancient-wisdom-lds-temple.blogspot.com/ that talks about how the Christians around the time of the Savior viewed Jesus Christ as the temple High Priest (see Hebrews 4:14-15). Here are the highlights:
"The earliest Christians viewed Jesus Christ in the role of the High Priest of the temple (Hebrews 3:1; Hebrews 5:10). He is even described as wearing a seamless robe similar to the one worn by the high priest (John 19:23; compare Exodus 28:31-32). He pronounced a blessing on his disciples after the manner of the high priest with uplifted hands (Luke 24:50; compare Leviticus 9:22-23; Numbers 6:23-27. He was baptized at age 30, which was the age when temple priest began to serve (Luke 3:21-23; compare Numbers 4:1-4). The prayer that Christ utters in the seventeenth chapter of the book of John is regarded by many biblical scholars to be a high priestly prayer. Christ is also depicted in Revelation 1:12-13 standing in the heavenly temple wearing 'the royal and high-priestly garb.' (see The Gate of Heaven, Matthew B. Brown, pg. 168-169)"