Why is Christ's substitutionary death important?

The importance of Christ's substitutionary death lies in its role in satisfying the demands of God's law, as He bore the penalty for sin that we deserved. Paul states in Romans 5:18 that through one man's disobedience many were made sinners, but through the righteousness of one, the free gift has come to all men unto justification of life. Christ died not for His own sins, but for the unjust (1 Peter 3:18), ensuring that God's wrath against sin was fully satisfied, allowing believers to be declared righteous before Him.