Opposite of "literal"

I was listening to the radio today, and someone said, "The couple came across a literal 'pot of gold.'" It made me think: how do you say the opposite of that? I'm looking for a statement or phrase that lets you know that an idiom is an idiom and not to be taken "literally."

Figurative or metaphorical are my go-tos

Both are essentially the same, as you can see from many dictionaries using one to define the other. When I get home I'll consult a more accepted source than Google, but I'm sure they won't have much to add.

Figurative:

departing from a literal use of words; metaphorical.

Metaphorical:

characteristic of or relating to metaphor; figurative.

The opposite of 'literally' is literally... literally!

According to the Oxford dictionary, literally now has two definitions,

The traditional meaning:

In a literal manner or sense; exactly:

‘the driver took it literally when asked to go straight over the roundabout’

Or, the informal meaning:

Used for emphasis while not being literally true:

‘I have received literally thousands of letters’

So, depending on the context and emphasis, you could say the following:

The couple came across a literal 'pot of gold' when they bought their new house, and found it included a bucket of 16th Century silver coins.

And literally be grammatically and syntactically correct!

"Figurative", "Metaphorical", and "Proverbial" all spring to mind.

Figurative language is a general term describing anything in language that has a meaning other than its literal meaning--this is probably your best bet ifor a direct antonym of "literally." Note that the distinction between literal and figurative language exists within the field of language analysis independently of the contradictory dictionary definitions. Therefore, I am using "literally" here in its traditional meaning.

Metaphors are a specific figurative construct in which one entity is referred to as another entity in order to describe its properties. In your case, the couple found an actual pot of gold, but if they had stumbled across, say, an extremely valuable collection of ninth century Chinese porcelain, their find could still be described as a pot of gold to explain how valuable it was.

Proverbs are common sayings, often embodying a truth (eg. "A rolling stone gathers no moss"). I'm not sure if this usage is strictly correct, but I've heard it used on numerous occasions (for example, on Star Trek: The Next Generation, whenever the android Data used figurative language, he prefaced it with "proverbial" to explain that what he was about to say was not meant to be taken literally, e.g., "a proverbial needle in a haystack"). I believe that proverbial would be appropriate in your case, as "pot of gold" is a universally known saying within American English (possibly British English?), but I do not believe it would be appropriate if you were trying to establish the non-literalness of an arbitrary phrase with no cultural roots.