What does it mean that Jesus Christ is the cornerstone?
The Book of Isaiah has many references to the Messiah to come. In several places He is referred to as “the Cornerstone,” such as in Isaiah 28:16-17: “So this is what the sovereign Lord says: ‘See, I lay a stone in Zion, a tested stone, a precious cornerstone for a sure foundation; the one who trusts will never be dismayed. I will make justice the measuring line and righteousness the plumb line.’” God is speaking to scoffers and boasters when He refers to the Cornerstone—His precious Son—who provides the firm foundation for their lives, if they would but trust in Him. Isaiah uses construction terminology (measuring line and plumb line) to make his point; these are things the people would understand.
In the New Testament the cornerstone metaphor is continued. This time, however, the apostle Paul is preaching to the Ephesian Christians for the purpose of helping them know Christ better. In chapter 2, verses 19-21, the comparison between Jesus and Cornerstone becomes very clear: “Consequently, you are no longer foreigners and aliens, but fellow citizens with God’s people and members of God’s household, built on the foundation of the apostles and prophets, with Christ Jesus himself as the chief cornerstone. In him the whole building is joined together and rises to become a holy temple in the Lord.” Furthermore, in the 1 Peter 2:6, what Isaiah said centuries before is affirmed in exactly the same words.
Christ is the Head of the Church which is the Body of Christ
The stone that the builders rejected has now become the cornerstone.
Then Jesus asked them, "Didn’t you ever read this in the Scriptures? ‘The stone that the builders rejected has now become the cornerstone. This is the LORD’s doing, and it is wonderful to see.’
Simon Peter replied, "Lord, to whom would we go? You have the words that give eternal life.
Jesus is the foundation, we need set up on Him. We need follow Him and like him.