What is the significance of the Memorial?
Jesus used this opportunity to teach them true humility, real love and warned them of tribulations they would be facing. After the meal was over, and Judas Iscariot had left, to the faithful eleven, Jesus said: "Keep doing this in remembrance of me." (Luke 22:19) Later, the apostle Paul would write to members of the spirit-begotten Christian congregation: "As often as you eat this loaf and drink this cup, you keep proclaiming the death of the Lord, until he arrives." (1 Corinth. 11:26) The Memorial calls special attention to the meaning of Jesus death in working out Jehovah's purpose. It highlights the meaning of Jesus sacrificial death especially in relation to the new covenant and to the way that his death affected those who will be heirs with him of the heavenly Kingdom.
(John 14:2, 3; Heb 9:15)
The Memorial is also a reminder that Jesus' death and the way it was accomplished, in harmony with God's first prophecy at Genesis 3:15, served to vindicate Jehovah's name. By maintaining integrity to Jehovah down till his death, Jesus proved that Adam's sin was not due to any flaw in the Creator's designing of man but that it is possible for a human to maintain perfect godly devotion even under severe pressure, and thus Jesus vindicated Jehovah God as Creator and Universal Sovereign. Besides that, Jehovah had purposed that Jesus' death would provide the perfect human sacrifice needed to ransom Adam's offspring, and thus make it possible for billions who would exercise faith to live forever in a paradise earth, in fulfillment of Jehovah's original purpose and in expression of his great love for mankind. -John 3:16; Gen 1:28
What a tremendous burden rested upon Jesus on his last night on earth as a man! He knew what his heavenly Father had purposed for him, but he also knew that he had to prove faithful under test. Had he failed, what a reproach it would have meant for his Father and what a loss to humankind! Because of all that would be accomplished by means of his death, it was most fitting that Jesus instructed that it be memorialized.
Information from: Reasoning From the Scriptures page 266, paragraph 1 thru page 267, paragraph 1