The verb “to be,” when used with a predicate, expresses equivalence. “I am Paul” indicates that “Paul” has the same meaning as “I.”
“To be” without a predicate is different. When Descartes says, “I think, therefore I am,” or when Hamlet ponders whether “to be or not to be,” the verb expresses existence, not equivalence.
After God called Moses to free the children of Israel from bondage, Moses asked for His name. Here is the response he received:
God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you.Exodus 3:14
It’s a curious grammatical construction, and it emphasizes God’s independent existence. Furthermore, the Hebrew word for “I am” in this passage—ehyeh (אֶֽהְיֶ֣ה)—is in the imperfective aspect, which indicates something that is ongoing, something that is not yet finished. In other words, it carries the connotation, “I exist, and I will continue to exist.” Here’s how Elder D. Todd Christofferson described it:
The Savior is not dependent on food or water or oxygen or any other substance or power or person for life. Both as Jehovah and Messiah, He is the great I Am, the self-existing God. He simply is and ever will be.“The Resurrection of Jesus Christ,” General Conference, April 2014
During the Savior’s mortal ministry, He told a group of people that Abraham had seen His life and had rejoiced in it. They responded critically, “Thou art not yet fifty years old, and hast thou seen Abraham?” Jesus replied, “Verily, verily, I say unto you, Before Abraham was, I am” (John 8:57-58). His listeners recognized the allusion to the Exodus passage above, and they knew that He was declaring Himself to be the God of Moses. They were outraged and tried to stone Him for blasphemy, but He escaped.
In the Book of Mormon, God does not identify Himself as “I am” without a predicate, but Jesus Christ did emphasize His eternal nature when He introduced Himself to the people following His death and resurrection: “I am Alpha and Omega, the beginning and the end” (3 Nephi 9:18). This echoes His introduction in the Book of Revelation:
I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty.Revelation 1:8
Today, I will place my trust in the God who is, and who was, and who is to come. I will remember that in a world of change and instability, He is a constant whom I can rely upon, the self-existing God who will always be there.