There’s a difference between what words refer to and the way we use words.
To say that something is ‘concrete’ or ‘abstract’ is to talk about the nature of the things that are being referred to (by our words). To say that a passage should be understood in a ‘literal’ or ‘metaphorical’ way is to note the way the words are being used.
For example, Plato’s theory of forms is a LITERAL reference to an ABSTRACT theory. On the other hand, that “old tin can” would be a METAPHORICAL description of a CONCRETE item i.e. my car.
Also, just because someone may state that Biblical passages talking about the Second Coming of Christ have to be read metaphorically, this does NOT mean that the events to which they refer are necessarily abstract. Likewise, there is sometimes the idea that unless a passage is taken literally, the referents of said passage are ‘not real’ or they ‘did not occur’ i.e. we need to be wary of certain ways of reading which is overly skeptical of the use of metaphor as these readings may disguise a failure to understand that writers may discuss very concrete events but use words and pictures creatively.
Eg,Christ’s return will be ‘earth-shattering’ is metaphorical but in no way implies that it’s “merely spiritual” or cannot be understood of present socio-political consequences — nevertheless, it’s poor hermeneutics to begin associating this event with, say, cracks in the earth’s crust…