The Holy Eucharist is the body and blood, soul and divinity of Christ. This is not symbolic, allegorical, metaphorical, or merely spiritual. Christ is really present in the Eucharist, which is why it is also called the Real Presence.
It is easy to see why this sacrament is the most central and important to Catholics. When we consume the physical Eucharist it becomes part of our bodies while our souls are being nourished by the reception of Christ personally and totally.