A sacrament is a channel of God’s grace.
What does this mean?
Like a farmer in the desert digging an irrigation channel to bring water to his crops, God channels his grace to us through the sacraments of the Church. Without water, the farmer’s plants will wither and perish. Similarly without prayer and the sanctifying grace of the sacraments, we are left spiritually under-nourished and weakened.
So a sacrament is not a symbol, a metaphor or an empty ritual. It is a real power of God. And the more we open our hearts, our minds, and our lives to it, the more powerful it is in drawing us closer to Him.