Sanctification is the process by which we actually begin to become holy, free of the effects of evil and full of charity or divine love.
For example, Cyril of Alexandria, writing in the early fifth century, describes mystical union with God through the widely used image of iron heated in fire:
"To participate in the divinity of the Son . . . is . . . to be penetrated by divinity — just as the red-hot iron in the fire is penetrated by the heat of the fire — allowing the beauty of the inexpressible nature of the Trinity to shine in us."
As fire causes iron to glow, so too does the Holy Spirit enable the divine life of the Trinity to show itself in our life of love.
— Diogenes Allen, Spiritual Theology