The bread of the Lord’s Supper replaces the Bread of the Presence, and in it Christians have a sign of God’s invisible presence within the visible signs of bread (and wine).
When instituting the Lord’s Supper, Jesus cited Exodus 24–25. In these chapters, Moses and the elders feasted with God in heaven, made the covenant with blood, saw the heavenly tabernacle and then replicated it on earth (which includes the bread as eternal covenant offered as a memorial), the wine flagons, the menorah, and other elements within the tabernacle.
The bread, in particular, played a key role in Israel’s religion. Every Sabbath priests used to offer the twelve loaves of the bread of the presence before enjoying the meal with the bread. The bread of presence literally translates as “bread of face” (lechem panaim).
“Bread of face” probably refers to YHWH’s presence. So the loaves represent the visible presence of the invisible God, with the light of the tree (menorah) shining upon the twelve loaves that represent Israel (cf. Num 6:25).
Let me outline how this works step-by-step and then conclude by asserting how this Old Testament background leads to a keener understanding of Christ’s Spiritual or real presence at the Lord’s Supper. And as a general rule, my argument follows Brant Pitre’s book Jesus and the Last Supper.