We can go back to Saint Thomas Aquinas to explain the Eucharist with these two quotes from Summa Theologiae Part III:

“Bread and wine are the proper matter of this sacrament. And the reasonableness of this is seen, first, in the use of this sacrament, which is eating: for, as water is used in the sacrament of Baptism for the purpose of spiritual cleansing, since bodily cleansing is commonly done with water; so bread and wine, wherewith men are commonly fed, are employed in this sacrament for the use of spiritual eating.”

“Yet this change is not like natural changes, but is entirely supernatural, and effected by God’s power alone. . . . Hence this is not a formal, but a substantial conversion: nor is it a kind of natural movement: but, with a name of its own, it can be called transubstantiation.”

The controversy of the Real Presence goes right back to the disciples who knew Jesus 2000 years ago when he walked among them:

Then many of his disciples who were listening said, “This saying is hard; who can accept it?” Since Jesus knew that his disciples were murmuring about this, he said to them, “Does this shock you? What if you were to see the Son of Man ascending to where he was before? It is the spirit that gives life, while the flesh is of no avail. The words I have spoken to you are spirit and life. (John. 6:60-63).

Bishop Barron explains how Jesus was given the opportunity to present this in a metaphorical or symbolic way, instead He intensifies His language. He says “amen amen I say to you..”, that’s biblical code for what I’m saying is really important, “Unless you eat the flesh of the Son of Man and drink His blood you have no life within you”. He intensifies by saying “My flesh is real food, my blood is real drink”.