Eating blood is FORBIDDEN throughout Scripture and the command is reiterated, guided by the HOLY SPIRIT, at the Council at Jerusalem.
Acts 15:28-29 For it has seemed good to the Holy Spirit and to us to lay on you no greater burden than these requirements: that you abstain from what has been sacrificed to idols, and from blood, and from what has been strangled, and from sexual immorality. If you keep yourselves from these, you will do well. Farewell.”
If it was to be taken literally that Jesus was commanding people to eat his flesh and blood, He would be commanding them to break the very Law that He handed down to them at Mt Sinai. IOW, He would be commanding them to sin.
Not to mention that Jesus HIMSELF says it's a metaphor.
Right here, at the end of John 6.
John 6:63 It is the Spirit who gives life; the flesh is no help at all. The words that I have spoken to you are spirit and life.
The SPIRIT gives life, not eating.
The flesh is no help at all.
It's NOT physical eating of actual flesh.
Jesus said to them, "Very truly I tell you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. John 6:53
it seems to say we need to eat his flesh. He turned bread into his flesh, so we may eat it.
What part do you not understand?
It’s really easy to figure out why Jesus is speaking metaphorically.
If it is so easy to figure out why Jesus is speaking metaphorically, it would seem that there would be evidence that some Christians who lived during the first 1500 years of Christianity believed this to be true.
Are you aware of any such evidence?