What does John 12:18 mean?

Jesus' miracles are described in the gospel of John as "signs." Like a carved or printed road sign, these are meant to provide some specific message, or direction. In the case of Christ's miracles, that message is that He is the Son of God, and we are meant to believe in His message (John 20:30–31). Scripture shows us that many people reacted to Jesus and His miracles, but not many seem to have correctly understood them. When Jesus fed thousands in a miracle (John 6:9–14), the people were more concerned with free food and political issues than spiritual truth (John 6:15, 26). Confronted with a more accurate understanding, many turned away from Christ (John 6:66).

Many of the people cheering for Jesus during this triumphal entry (John 12:12–13) are excited because they've heard about His recent accomplishment: raising Lazarus from the grave after four days (John 11:38–44). Those same people are aware of Old Testament promises of a Savior, who will free Israel—much of the shouting and praise being spoken echoes those prophetic passages (John 12:14–15). However, just as the people who saw Jesus multiply food are distracted by material things, many of the people cheering for Jesus in Jerusalem are misguided. They're excited to see a worldly conqueror—a social savior—rather than Scripture's full picture of what Messiah will be (Isaiah 53:3–6; Mark 8:31; Luke 17:25).

This mob also stokes the fears of Jerusalem's religious leaders. Earlier, they'd committed to having Jesus killed to prevent Him from arousing the anger of Rome (John 11:45–53). Seeing the people openly hail Jesus as their king suggests those fears were valid.