Isn't that an odd position to take when parts of the Bible insist that it is not metaphorical? (e.g. Paul's argument in 1 Corinthians 15 about why he believes in Jesus' bodily resurrection and his conclusion that "If we have hoped in Christ in this life only, we are of all men most to be pitied.") I can understand those who believe the Bible to be true (mixed in with some metaphor) and I can understand those who do not believe it to be true. It seems odd, though, to believe that it is entirely metaphorical and decide to take it seriously, given some of what it says.
In Romans 7, Paul makes the argument that he cannot set himself free from sin and he needs God. If you believe the Bible is entirely metaphorical but take it seriously, do you believe you are setting yourself free?