Metaphors are used in interfaces all the time. The metaphor of the desktop is perhaps the most commonly cited. We don’t talk about the desktop a lot these days, but the collective we does talk a ton about the skeuomorphism that is running rampant in Apple’s various products. Your opinion on that topic may vary, but I’ll take stab in the dark and say your opinion of the Microsoft Briefcase is either 1) what is that? or 2) ugh that’s a terrible metaphor (fun fact: Briefcase is available in MS Windows 7, but has finally been retired from Windows 8. A sad day indeed…)
Metaphors in gaming interfaces are used frequently too, and not always well. Grand Theft Auto IV makes frequent use of a cell phone for contacting other in-game characters. Being set in 2008, as text messaging was on the rise, this totally makes sense. Unfortunately, being an appropriate metaphor doesn’t mean that it’s an easy to use interface, and here’s where the game runs into all kinds of trouble.