(Wow, I'm blogging a lot these days, aren't I?)
I had forgotten how beautiful Beowulf is as a literary creation. We studied it senior year of high school and I remember the teacher introducing us to the literary device known as a kenning. A kenning is effectively another comparison - like simile and metaphor. For me, the only way to really understand it is to think of simile, metaphor, and kenning not as equal, but as degrees of impact. Simile, the smallest degree, uses the words like or as; metaphor, which is a super-simile, just uses the word is; and kenning, a mega-metaphor, uses neither like nor is.
A kenning in Beowulf is the "swan's road." That's all the poem says - swan's road. It means the sea, but nowhere in the sentence will you find the word sea. The kenning, sadly, has fallen out of use in the literature of the English-speaking world.