Let me use the example of our legal laws in the United States. When you read the laws, they mean what they say. Over and over courts and judges have taken little pieces of previous court cases, and interpreted what the actual words say, to be applied to their particular new court case.

Regarding the Bible, while it might be difficult to understand what is being said regarding literal and metaphorical, usually the explanation is right in front of us. For example, if the Bible says something like, "I saw what looked like a ...," the wording itself is stating that the following parts are figurative. They state it in the words "look like." Then, when you watch the punctuation for a new thought, and it says something like, "Then I saw an angel coming down...," there is a change from the figurative to the literal.

Unfortunately, God is so much greater than we are, that His operations can barely be made simple enough for us to understand. For example, playing chess is relatively easy. Knowing how to win or at least draw from every "play" is not so easy. We are finding that computers can be built to beat even the greatest chess masters, in every game. So, why would we think that we can understand everything that God says in a universe that is many times more complex than a chess game?

The point about the Bible is, there is that which is literal, and can be understood by almost anyone. There is part that is figurative and can be understood by almost anyone. But there are going to be parts that will not be understood easily, and maybe a few that will not be understood at all, but are there just to show the greatness of God.