Christ sometimes speaks literally, and sometimes He uses metaphor and parables.
Was He speaking metaphorically when He commanded His disciples to eat His body and drink His blood?
No, He meant His words to be taken literally.
How do we know this? I can think of two reasons, though I don't doubt that there are others:
a) As well as speaking of His Body and Blood in Capernaum, Christ instituted the Eucharist at the Last Supper.
And He took the bread, gave thanks and broke it, and gave to them, saying, "This is My body, given for you; do this in remembrance of Me."
St Paul corroborates the true nature of the Eucharist in several passages. For instance:
When we bless the cup at the Lord's Table, aren't we sharing in the blood of Christ? And when we break the bread, aren't we sharing in the body of Christ?
And also:
For those who eat and drink without discerning the body of Christ eat and drink judgment on themselves.
b) When Christ told his disciples that they must eat His body and drink His blood, many of them left Him.
If Christ was speaking metaphorically, why did they leave Him?
If they simply misunderstood His words, then why didn't Christ call them back to explain what He really meant?
Hope this proves helpful.
Christ told the rich young ruler to do so.
He did not chase after Him.
We do not see Christ chasing the unbelieving Pharisees either.
If Christ was speaking metaphorically, why did they leave Him?
You ask a good question but let's keep things in context.Notice He asked them several other questions.
60Therefore many of His disciples, when they heard this said, “This is a difficult statement; who can listen to it?” 61But Jesus, conscious that His disciples grumbled at this, said to them, “Does this cause you to stumble? 62“What then if you see the Son of Man ascending to where He was before?
63“It is the Spirit who gives life; the flesh profits nothing; the words that I have spoken to you are spirit and are life.
Jesus clarifies His words to them as being Spirit and life...not literal words.
Now He returns to where the conversation was before the discussion with the unbelieving Jews. It's back to believe in Him.
64“But there are some of you who do not believe.” For Jesus knew from the beginning who they were who did not believe, and who it was that would betray Him.
65And He was saying, “For this reason I have said to you, that no one can come to Me unless it has been granted him from the Father.”
66As a result of this many of His disciples withdrew and were not walking with Him anymore.