Protestant Christians believe that Jesus was speaking metaphorically in John 6 and in the gospel accounts of the Last Supper in the same way that he speaks metaphorically when he calls himself the light of the world (John 8:12), or the sheep gate (John 10:7-9), or the good shepherd (John 10:14). Did he speak literally? No, it is clear that he is not a light, or a gate, or a shepherd in the literal sense … he is only speaking metaphorically. They believe that he is referring to the bread and wine in that same metaphorical sense.
The Catholic response? Jesus says this in John 6: “… the bread that I will give is my flesh for the life of the world.” (John 6: 51). Jesus also says this in John 6: “… unless you eat the flesh of the Son of Man and drink his blood, you do not have life within you.” (John 6:53). And he says this: “Whoever eats my flesh and drinks my blood has eternal life, and I will raise him up on the last day.” And this: “Whoever eats my flesh and drinks my blood remains in my and I in him.” (John 6:56). After all this teaching, “many of his disciples returned to their former way of life and no longer accompanied him.” (John 6:66). But did he stop them? Did he explain that he was only speaking metaphorically? No, they walked away and returned to their former way of life.
And St. Paul’s reinforcement? St. Paul repeats the words of the last supper (without having had the benefit of reading those words in Scripture, since they had not yet been written down). (1 Cor 11:24-25). And then he says this: “For anyone who eats and drinks without discerning the body, eats and drinks judgement on himself.” (1 Cor 11:29). St. Paul thus says that he believes that the bread and wine are the literal body and blood of Christ. And this is how it was for 1500 years until the Protestant reformers came along and made a new interpretation, telling people that it was only a metaphor … something neither Christ nor St. Paul did.
So in the Catholic Church, the Eucharist is the centerpiece. Not the sermon. Not the singing. Not the personality of the preacher. The Eucharist. In the words of Allen Hunt, a former Protestant mega-church minister who converted to Catholicism: “The Eucharist binds us together. Without the presence of Jesus in the Eucharist, we merely have our own ideas rather than true unity. In the Eucharist, Jesus fuels and empowers his church. Everything rides on the Eucharist.” Amen, Mr. Hunt!