Watch: Rory Kinnear on how he made his characters in Men
The film follows Buckley's character Harper as she retreats to a quiet country house in an attempt to deal with the death of her husband (Paapa Essiedu), who died in an apparent suicide after a row in which he hit Harper.
But there's something amiss in the rural village, in which every man shares the face of Kinnear — including a nine-year-old boy rendered with deliberately uncanny valley CGI — and they all seem to be unnerving in their own ways.
"In the script itself, you knew that these characters were representations of particular figures of society and figures of authority," Kinnear told Yahoo.
He said: "But you wanted to make sure that you fleshed them out and made them as credible and that they existed within this world and within this rural landscape as much as the natural world was going to figure as well."
Kinnear said that Garland was 'pretty open' in giving his actor the latitude to shape his array of at least eight or nine different characters and find the nuances in their particular brands of male toxicity.
"I wrote biographies for each of the characters and sent them off to [Garland]," said the 44-year-old star.
Kinnear added: "He then sent them off to hair and make-up and wardrobe, so it was very much a collaboration until we got to set.
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"Even on set, he was up for further provocations from both of us, so it was a really fun, creative time in that respect."
That creative atmosphere was enhanced by the fact the cast and crew had to remain close-knit due to the impact of COVID-19 restrictions during the 2021 shoot.
Kinnear said this closeness, between himself and Buckley especially, helped to keep spirits high, particularly when the material was at its darkest.
"I think the harder the stuff that you have to film, the stronger the release valve," he said.
Kinnear added: "Obviously we were filming during COVID, so it was basically just the two of us both at work and then at the hotel as well.
"We were pretty much the only people staying in this very haunted-seeming country hotel and then going to this haunted-seeming country house to work all day. So you had to make sure you laughed as well, otherwise, it would be glum town."
The film has achieved strong reviews since its recent premiere at the USA and screening at the Cannes Film Festival, with Garland again earning praise after his previous directorial efforts Ex Machina and Annihilation.
Men will be released into UK cinemas on 1 June.
Watch: Trailer for Alex Garland folk horror movie Men