ART AND CREATION
Obviously, the main "big idea" at play here in the most direct and human terms is to present an extreme horror-movie version of the pain, frustration and resultant negative behaviors of an artist struggling to remain inspired, and failing to maintain a proper distance between one's fans and personal life. To drive the point home (and, perhaps, to mitigate the inevitable self-regarding narcissism that tends to come from artists - especially filmmakers - getting metaphorical about art-creation) it all plays out not through the artist's perspective, but through the even more painful experiences of an artist's partner. Lawrence's character gradually discovers that their need to create will mean whatever love you share will eventually be processed into "creations," which they will give up to be consumed by their fans in exchange for praise worship - even creations that seemed to arise from the personal connection between them.
In terms of authorial self-reference, you could easily view the film as an act of self-punishment as confession - an artist/filmmaker's confession at being callous and self-involved in their work and forsaking of their loved ones in the pursuit of praise and acceptance. Bardem's poet takes his wife's hard work of keeping his world in order to be flattered by fans, lets them (literally) tear off and keep pieces of his life, and ultimately even what should be a precious creation between he and his wife that matters more to her than it ever can to anyone else is still just another thing he can let his fans consume. Ultimately, he takes everything from her in order to feed his need to create, and even if she finds an escape he'll still take the best of her as a (literally) crystallized memory to inspire him.
Or, if you want to put it more bluntly: It's difficult (especially given how hard the "intensely personal" aspect of the film's meaning has been hyped leading up to it's release) not to see mother! as Aronofsky "owning up" to perhaps having been not the most wonderful person to be in a relationship with during his especially creative periods. Granted, it's just as plausible that the director is making reference more broadly to the difficulties all creative people sometimes encounter in managing the work/life balance. But the last time Aronofsky mused on the subject of women who become muses to driven men was The Fountain - where the muse (or muses - its a complex film) in question was embodied by his now-ex (as of 2010) wife Rachel Weisz. That film was followed by The Wrestler and Black Swan, both also about creative-performers whose drive and need for praise consume their lives and relationships, and Noah - a reimagining of the ultimate inspired-from-above construction project yarn.
Oh, and he (Aronofsky) also happens to be currently in a relationship with Jennifer Lawrence, whom he is exactly as many years older than as Javier Bardem.
THE HOME AND THE WORLD
While it's hard not to read a heavily-metaphorical film from a famously high-minded filmmaker on the subject of the artist's process as being "only" about their own torment, it's notable that mother! frames the artist in question as a kind of self-pitying, childish monster... and also not as the main character, giving the narrative point-of-view entirely over to Jennifer Lawrence as the mother (her official screen credit - no capitalization) of the title.
In a sense, this makes the film akin to a perspective-reversal on the Stanley Kubrick version of The Shining, which also happens to be about a writer alternately neglecting and destroying his family in the pursuit of creative inspiration. As with mother!, The Shining's isolated single-location setting (The Overlook Hotel) is often read in symbolic-interpretations as standing in for "the world" in terms of the place characters come to occupy within it: Jack Torrance as patriarchy/fatherhood reigning in tyranny over women (his wife Wendy) and children (Danny) despite holding only tangential "authority" over the place, egged-on by justifications offered by the (literal) ghosts of the past. The Overlook happens to be built on a desecrated Native American burial ground, in case you thought that specific metaphor wasn't built into the text.
Likewise, mother! seems to be playing out a version of the same "contained world" conceit within The Poet's home... but with the extra wrinkle that "mother" herself and the house/world appear to comprise a single character. She's the only character who is never seen leaving the house (not even stepping off the porch) and reacts with physical pain when people make a mess or parts of it are destroyed. This is, of course, literalized once the ending reveals that generating a fresh "mother" to inspire Him,and conceive new works for his followers is part of the house/world's regeneration cycle: the world is the house is the woman is the world.
As is also the case with The Shining, there's a societal-abuse-of-women aspect to this, with The Poet's cultists going from dismissing his wife as part of the scenery to beating and sexually-degrading her; to say nothing of the idea of venerating motherhood while treating mothers themselves as vessels to be discarded, and children as literal grist for the societal mill. On that same track, Aronofsky also happens to be a passionate environmental activist (Noah reimagined the Biblical Flood as divine punishment for antediluvian ecological destruction, with Noah and his family of designated-survivors as nature-loving prehistoric vegans), and that same view of mankind as a plague on the planet seems wedded to the portrayal of fandom as life-devouring horde: When "mother" demands to know why her husband's fans are pulling apart the house for keepsakes, one explains: "To prove I was here!"
And then there's that capital "H" on Him...