Answer:
Your question creates what is sometimes called a false dichotomy. The false dichotomy is this: Either Jesus was “literally” the son of God, or he was merely God’s son metaphorically. First of all, if we use the standard definition of fatherhood, Jesus was not literally the son of the Father, for the simple reason that God the Father does not take physical form. He is not a male person with male genitalia. The Muslim will therefore argue that Jesus was not literally God’s son.
The problem with this argument used by Muslims is the way that they are using the word “metaphorically.” What would it even mean to say that Jesus of Nazareth was God’s son “metaphorically.”? I do not even know what that would mean.
Here is what I know. John 1:1 In the beginning was the Word. The Word was with God (the Father), and the Word was God (the Son). In John 1:14 we are told that this Word of God took on flesh and lived among us in an actual human form. This same “Word of God” is then called God’s Son. He is God’s only-begotten, unique Son. What does this mean? I will admit that I cannot precisely explain what it means that Jesus is the unique “Son” of God, but it is certainly not a mere metaphor. The sonship of Christ is not mere metaphor. That is for sure. Jesus really is God’s Son. But he is not “literally” (in the human sense of literally) the son of God.
My answer is this: Jesus is neither literally God’s son, nor is he merely “metaphorically” God’s Son. Jesus truly is the Son of God, but not a son in the human physical sense.
Let me illustrate my answer through use of a scene in the Book of John. It happens in John 10:30 when Jesus told his hearers that “I and the Father are one.” Did he mean that literally or metaphorically? Did he mean that he and God were really tight, like any other human could be really close to the Father (ie as a mere metaphor), or did he mean this in a special, unique sense? The answer is provided for us. When Jesus made this statement, the people took up stones to stone him. Jesus asked which of his marvelous works brought on the stoning. The answer they gave Jesus is this: “We are stoning you because you, a mere man, claim to be God.” Obviously, Jesus did not deny their contention that he was God. In this case, Jesus’ being one with the Father was clearly not merely metaphorical. I would say that this situation is similar to the one above. Is God literally God’s Son, or is his sonship merely that of a human who is very close to God. The answer is that Jesus is God’s son in a completely unique way which, if it were claimed and not true, would lead to him being stoned to death.