Science fiction is, among other things, the literature of talking about things you’re not talking about. It can be easier to grapple with the seductive nature of tribalism when you’re dealing with Mars vs. Earth. You can use the suffering of asteroid miners to ruminate on class conflict and worker exploitation without appropriating the lived experience of real people. Like horror or fantasy, science fiction is a literature of literalized metaphors.
In that context, aliens become vessels that can hold many different cargos. An alien can be a lost traveler from the stars desperate to save a dying home planet, an invader bent on the destruction of humanity, an incomprehensible oddity that assaults the nature of reality, a victim of human colonialism, the re-imagination of ancient Babylon as seen by the peoples they conquered or any of a thousand other things.
Many of the best works of science fiction drop a net into these waters and come up with very different — and often wonderful — catches. Here are some of our favorites.