Jesus also said He was the Vine, and the Door. Why couldn't His reference to bread and wine be figurative?
I'll give one Old Testament and two New Testament reasons.
The Old Testament is a prefigurement of the New. The Jews had to eat the Passover Sacrifice. Here Christians have to eat the Passover sacrifice - the body and blood of Jesus.
In the New Testament the 3 synoptic Gospels all have the clear institution of the Eucharist, where Jesus says “This is My body which is given for you; do this in remembrance of Me” & “This cup which is poured out for you is the new covenant in My blood.". Now if you look at the Gospel of John he doesn't have the last supper in his Gospel. John instead discusses the feeding of 5,000 for truth of the real presence.
Jesus said to them, “I am the bread of life; he who comes to Me will not hunger, and he who believes in Me will never thirst...
“Truly, truly, I say to you, he who believes has eternal life. “I am the bread of life. “Your fathers ate the manna in the wilderness, and they died. “This is the bread which comes down out of heaven, so that one may eat of it and not die. “I am the living bread that came down out of heaven; if anyone eats of this bread, he will live forever; and the bread also which I will give for the life of the world is My flesh.”...
Then the Jews began to argue with one another, saying, “How can this man give us His flesh to eat?” So Jesus said to them, “Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in yourselves. “He who eats My flesh and drinks My blood has eternal life, and I will raise him up on the last day. “For My flesh is true food, and My blood is true drink. “He who eats My flesh and drinks My blood abides in Me, and I in him. “As the living Father sent Me, and I live because of the Father, so he who eats Me, he also will live because of Me. “This is the bread which came down out of heaven; not as the fathers ate and died; he who eats this bread will live forever.”
Here Jesus, says he is bread of life. The Jews grumble. Then he goes one step further saying that he is the bread and that you have to eat of this bread. The Jews began to argue. So Jesus goes full bore. He says truly, truly - i.e. I am literally saying unless you eat (and the word eat used in John is the word to gnaw like an animal on a bone) the flesh of the Son of Man and drink His blood, you have no life in yourselves.
So what happens? Many of his followers leave him. Now does Jesus stop them or clarify his teaching? Nope. He doubles down again. He turns to the 12 and asks them are you going to leave also? He doesn't back down, he doesn't clarify. He meant exactly what he said.
The most ironic thing I have found in the bible is that those who turned away from believing that Jesus is truly present in the Eucharist is this verse:
As a result of this many of His disciples withdrew and were not walking with Him anymore. John 6:66 It is the only 666 verse in the new testament.
So how does the early Church view the Eucharist?
Therefore whoever eats the bread or drinks the cup of the Lord in an unworthy manner, shall be guilty of the body and the blood of the Lord. But a man must examine himself, and in so doing he is to eat of the bread and drink of the cup. For he who eats and drinks, eats and drinks judgment to himself if he does not judge the body rightly. - 1 Corinthians 11:27-29
If the Eucharist were symbolic, you could not be so bring judgment on yourself for being guilty of the body and blood of the Lord. However, if it truly is the body and blood of Jesus, then you could bring judgement on yourself if you eat it unworthily.