Monism must refer to something that actually exists. What is it?
Matter. Material monism is by definition referring to matter.
I am not sure what the confusion is here.
Every instance of Meaning must have something “that means”.
How is meaning related to ontology? Monism is a about what exists, not what something means. Semantics is the domain for this.
As I have said before, we ask what exists (ontology), how do we know (epistemology) and what is its meaning (semiotics). Together then we ask what is the meaning (semantics).
object metaphor theory 