What does the Bible say about the church's union with Christ?

The church's union with Christ is a central theme in John 15, where Jesus declares, 'I am the true vine, and my Father is the husbandman.' This metaphor illustrates the spiritual bond between Christ and His people, showing that just as branches draw life from the vine, so too does the church draw its spiritual vitality from Christ. The true church, as defined in the New Testament, consists of the elect whose names are written in the Lamb's Book of Life, highlighting that mere attendance or association with church buildings does not equate to being part of Christ's true body.