In this video Conversation, N.T. Wright emphasizes the importance of understanding the context of biblical texts in order to know whether to read them as literal or metaphorical narratives.
Wright begins by referencing the example of the Parable of the Prodigal Son (Luke 15:11-31) as an example of a text that is recognized not to refer to an actual historical event. We understand it as parable on account of its genre. Similarly, when Isaiah writes that the sun will turn dark, the moon will become blood, and the stars will fall from the sky, we know that this is not “a primitive weather forecast.”
Thus, we are able to distinguish between parable and resurrection narratives, and we know that apocalyptic texts are not weather forecasts. But with Genesis, the question remains of what clues we can find as to the author's intention –– or better, as to the author's "conceptual world" within which the narrative of Genesis makes sense. For additional perspective on this, see Pete Enns’s recent post on “genre calibration”.
Wright describes the use of biblical metaphor as “[the] language people use to refer to concrete events, but to invest those concrete events with their theological significance.” To use that framework then, the creation story becomes one where we can affirm some of the concrete events—the earth is created by a good God who has chosen human beings to be his image bearers on earth. But we cannot ignore the theological picture that the use of metaphor in Genesis adds to the text.