1 Nephi 1:9

"And it came to pass that he saw one descending out of the midst of heaven, and he beheld that his luster was above that of the Sun at noon-day."

The one descending with a "luster...above that of the sun at noon-day," is none other than Jesus Christ our Savior whom came to the earth for the purpose of saving all mankind. by the condescension of the Lord, we can choose to follow Him and gain eternal life or follow other paths. Jesus Christ condescended, or lowered himself, so that all may have the option to accept the Atonement.

By the expression of one having a luster brighter that noon sun it is saying His glory and power are beyond human comprehension. He is the Son of God and so His strength and power would be so great as to overpower the sun.