Not quite sure what people mean by expressions like "material beings", either. (I.e., it can similarly be an impediment with respect to proceeding any further.) I suspect "material beings" may fall out of naïve realism, but that's purely based on 99% of us using such words probably being commonsense realists either knowingly or unknowingly (tacit, implicit). Is "material beings" reference to mere representations or instead bold proclamations about non-mediated existence?
Corporeal objects -- those things which not only materialize in perceptions but thereby also have that appearance of existing outside themselves -- are representations associated with cognitive processes. Rather than those phenomenal entities literally being how "whatever is supposedly *outside* of consciousness" exists substantively slash in itself or exists independent of organism representations.
Materialist metaphysics, while just prescriptive speculation and dogma itself, would nevertheless usually seem to hold that what follows death or the termination of consciousness is not even nothingness (since "nothingness" would still be a background presentation of blankness, silence, empty feeling, etc). A return to what its matter is normally like -- i.e., it doesn't manifest and compare, period -- there is no "like".
Which is to say, going against that consequence of materialism, as commonsense or naïve realism apparently does in contending that there is an environment outside the head showing, discriminating, and conceptualizing itself just as in the head -- would actually be a tacit form of panpsychism, mentalism, monistic idealism, or whatever ontological claims along that line. The metaphysical version of "matter" ironically does not materialize as anything as it exists in itself or exists independent of cognitive products. That is, if its goal is to not be contaminated by mental (qualia and the generalizations, descriptions and symbolism of intellect / reasoning).
Arguably there alternatively is "materialism" as a systematic mapping and measuring of structural, functional, mechanistic or causal relationships that's abstracted (often with the aid of experiments) from the corporeal world manifestations of our experiences. But it is just that. A type of complex representing that's deliberately outputted by intelligence as opposed to the native and automatic operations of the senses. Not a metaphysical claim at all but just a humble epistemic tool or approach for predicting and manipulating the exhibited world.
Its version of matter revolves around quantitative properties rather than phenomenal slash aphenomenal characteristics. Such symbol-based description and ordinary technical language is yielded by mental processes and abides in its materializations (like other corporeal objects). David Hume's retrospectively labeled "pan-phenomenalism" at least tried to proclaim that impressions and overall "stuff that shows itself" was prior in rank to the arising or bundling of those manifestations as mind (thus dodging "mind" metaphysics). Products of intelligence certainly can't be non-artificial, but again this type of "materialism" isn't haughty metaphysical materialism. It's not making claims about lacking cognitive origins or being independent of such (identity-wise it would be in the same slot as para-religious materialism, if it was).
I mean seriously -- excluding cosmopsychism or Berkeley's god observing everything from all points-of-view (micro & macro levels) as the ultimate type of existence... The planet Mars could not exist in itself as a varying corporeal appearance from outside itself for a whole horde of reasons (especially including it lacking experiential capacities). And it certainly doesn't exist abstractly as various kinds of technical description according to whichever discipline. Those "rational objects" (as opposed to sense objects) typically touted as objective existence since ancient Greek days.
