Featured The two spellings of εἰμί in a third person singlar . . .

Taking metaphor literally just means they don't understand what a metaphor is.

 

Here is a definition: "metaphor Figure of speech in which a word or expression normally used of one object, action, etc. is extended to another" (P. H. Matthews, Oxford Concise Dictionary of Linguistics, p. 243).

Neither Greek nor English have any special grammatical or semantic way of presenting a metaphor. The thing about a metaphor is that it is presented in normal language. A metaphor states a comparison directly, though a simile may use "like" or "as."

What is important is what the metaphor is portraying. For example, in the metaphor "Lamb of God," there are important things that the metaphor is full of meaning about Christ: He is a sacrifice like a lamb is, He is meek like a lamb is, and so forth. If you can immediately see meaning in the metaphor, then it is not literal.

In the case of the Lord's Supper, one can immediately see figurative meaning: one must receive the Lord Jesus just as one receives the elements. That it was figurative is abundantly clear, because Jesus said, "This is my body," and "my blood," which statements were clearly impossible to interpret literally since the disciples could see His literal body with its blood intact right there in front of them.