Yes, this line is an example of metaphor. The language suggests at least some exaggeration and does not seem to be intended to be taken literally.
When trying to determine if a particular use of language is metaphorical or not, it is helpful to ask if the language in question was meant to be taken literally or not (or if it is even possible for the language to be taken literally).
This particular line is a bit problematic due to the ambivalent or fluctuating idea of the reality of god and/or the gods. Some people may read a line like this as a literal statement...but the fact that the term "Gods" is used, as opposed to "God", lends the line a quality akin to allusion.
Popularly speaking, references to "the Gods" in western literature allude to Greek and Roman gods, which are not generally thought to be actual or literal beings. They exist as concepts which are definitively literary and often metaphorical.
Yes, I believe that phrase is a metaphor.
Defination of metaphor: A figure of speech in which a term or phrase is applied to something to which it is not literally applicable in order to suggest a resemblance, as in “A mighty fortress is our God.”