If you review the various English translations of the phrase, you will get a good sense of the meaning behind what David wrote:
“I shall not want” (KJV, NKJV, NASB, ESV).
“I shall not be in want” (NIV).
“I shall not lack” (AMP).
“There is nothing I lack” (HCSB).
“I lack nothing” (Complete Jewish Bible).
“I have all that I need” (TLT).
“I have everything I need” (TLB, Good News Bible, TEV).
“I don’t need a thing” (The Message).
In essence, what David is saying with this little phrase is that we ought to put ourselves in the position of sheep, with a total and complete trust in a shepherd to provide everything we need; and therefore we have no lack. It is a cause-and-effect phrase: Since the Lord is my shepherd, I have everything I need, and I shall not want.
“All of us like sheep”
The problem with this thought is that we do not like the idea of being identified with sheep. Due to long-held stereotypes, we tend to think of sheep as being some of the stupidest animals ever created by God. We view them as dumb and largely defenseless! They have a tendency to wander into places that put them in danger. They require the care and protection of a shepherd, someone who will look after their smallest needs and who will lead them to where they need to be. This is not how humanity envisions itself.
Have you ever noticed there are no athletic teams named “The Sheep”? You do not usually think of courage and victory when you think of sheep. When the Lord called us sheep, it may be less than flattering, but it is certainly right on target!
The Hebrew prophet Isaiah compared our sin to that of straying sheep when he wrote, “All of us like sheep have gone astray, each of us has turned to his own way; but the Lord has caused the iniquity of us all to fall on Him” (Isaiah 53:6). Just like wayward sheep, we have a tendency to wander away from the right path that God has set before us in His Word.