A Metaphor is when you say something, but it means something else. Many Christians believe that parts of the Bible are metaphors, such as the part about stoning your children to death. Many Christians find Running their life based on Bronze Age and Iron Age texts would be difficult. Then some Christians avoid primitive parts of the Bible or tough parts of the Bible by saying they're metaphors of something or other.
Inevitably deciding what's literally true and what's metaphorical becomes arbitrary. This can lead to Christians deciding for themselves which parts of the Bible and which parts of Christian teachings they want to accept or letting their pastors decide for them.
Liberal Christians say quite a bit of the bible is metaphorical and liberal Christians often don't believe the parts of the Bible about Hell, and original sin are literally true. Christian Fundamentalists often insist that every word of the bible is literally true except clear parables.