Psalm 118:22, "The stone the builders rejected has become the cornerstone," is a powerful verse with layered meaning. Here's a breakdown of its significance:

Literal Meaning (in the context of the Psalm): In the context of the Psalm, it likely refers to the nation of Israel. They were often seen as weak and insignificant by the larger empires around them (the "builders" - like Assyria, Babylon, Rome), yet God had chosen them to be the foundation of His covenant and plan of salvation (the "cornerstone").

Metaphorical Meaning (the primary interpretation): The most common and important interpretation is as a prophecy about Jesus Christ.

The Rejected Stone: Jesus was rejected by the religious leaders of his time (the "builders" of Jewish society) and ultimately crucified. They considered him a threat to their power and a false messiah.
The Cornerstone: Despite their rejection, God raised Jesus from the dead and exalted him as the Messiah, the Son of God, and the foundation upon which the Church is built. He is the essential and most important part of God's plan for humanity. He is the chief cornerstone (Ephesians 2:20, 1 Peter 2:6-8) that holds the entire structure together. Without the cornerstone, the building cannot stand.

Theological Significance:

God's Sovereignty: It emphasizes that God can use what others deem worthless or insignificant for His great purposes.
Reversal of Expectations: It highlights how God often chooses the weak and humble to confound the wise and powerful (1 Corinthians 1:27).
Hope and Redemption: It offers hope that even after rejection and suffering, there can be resurrection and exaltation through God's grace.
Centrality of Christ: It underscores the absolutely essential role of Jesus Christ in salvation and the building of the Church.

In essence, the verse is a testament to God's power to turn rejection into triumph and to use the unexpected to fulfill His divine plan, ultimately centering on the pivotal role of Jesus Christ as the cornerstone of salvation.