What is an example of an epic simile in Beowulf?
"Epic simile" is also called Homeric simile, after its use in the Iliad and the Odyssey. As opposed to the standard simile, which tends to make a more straightforward comparison of "X is like Y," the epic simile is often much longer, makes more complicated connections, and may involve much less obviously related things, for the purpose of deeper imagery and emotional connection, as well as providing opportunities for the poet to momentarily shift their attentions to a side-lesson, such as a moral or historical point.
Most of the similes in Beowulf are short, although if we take the kennings into consideration as similes, they are abundant. One semi-epic simile is the brief diversion on line 1198 into the story of Hama: the poet compares the hoard of treasure gifted to Beowulf by Hrothgar to the theft of a necklace intended for the goddess Freyja by the hero Hama, who later escaped the persecutions of the evil king Eormenric and, supposedly, delivered himself into Christianity (another emphasis on the Christian themes that crop up throughout the text).
The most obvious, and perhaps only true use of epic simile in Beowulf is the "Father's Lament," which begins on line 2444, recounting how King Hrethel must feel in the aftermath of one son's murder by another, by comparing him to an old man whose young son is hanged. This passage gives numerous and detailed similes, such as everything feeling "too roomy" and feeling helpless because no aged wisdom or experience can restore the child to life. This is largely due to the fact that Hrethel, bound by the code of honor, can do nothing; such a murder would normally demand either payment or retribution, but he cannot execute his remaining son, nor pay himself for his own son's murder, and so he is left in a desolate and contemplative abyss of grief.