“Stray Dog” screens on Sunday at 7 p.m. at 4070 Vilas Hall, 821 University Ave. as part of the UW-Cinematheque series. Director Debra Granik and subject Ronnie “Stray Dog” Hall will both be in attendance to talk about the film. FREE!

I would not mess with Ronnie “Stray Dog” Hall. The Vietnam veteran and Missouri biker is a fearsome-looking man, the sort who looks like he’s led a hard life, but can make yours a lot harder. No wonder director Debra Granik asked him to appear in her movie “Winter’s Bone” as a terrifying backwoods drug dealer. (My interview with Granik is here.) In one deleted scene on the DVD, you can watch Hall absolutely let loose on John Hawkes with an improvised rant that includes the threat “I’ll nail your dick to the wall.” It clearly comes from someplace real.

And yet the man we meet in Granik’s first documentary, “Stray Dog,” is thoughtful, kind, respectful, and also quite sad at times. One of the most valuable things movies can do is put us in the shoes of someone we’d ordinarily never talk to — maybe never get up the nerve to talk to. Here, Hall reveals himself to the camera in a touching way, letting us see the man behind the bravado.

Granik takes a very cinema verite approach to documenting Hall’s life — there are no on-camera interviews, no voiceovers, no onscreen text to help us understand what we’re seeing. (In fact, I don’t think we learn Hall’s first name is Ron until we’re about a third of the way into the film.) Instead, the cameras follow Hall around, as he rides with his fellow bikers, goes to memorial services for his fellow veterans, and enjoys trailer-park domestic bliss with his wife Alicia and their dogs. Ron is the sort of man who needs people around him, needs people to depend on him.

As the cameras roll, we start to see Hall open up more, especially about the nightmares and memories that still plague him about the Vietnam War. He talks to a therapist for the first time, saying that he can’t forgive himself for the things he did over there, fearing that to do so would be a betrayal of his fallen comrades. Even though he knows, if he had the chance to ask his comrades, they would want him to forgive himself. In his mid-’60s, Hall is still a work in progress, trying to believe he is the good man others see in him.

The one major turning point in the film occurs when Alicia returns home from Mexico with two 19-year-old twin sons, Jesus and Angel, in tow. Hall is now a stepfather, and his tentative, polite, curious attempts to relate to his new family, trying to overcome the cultural and language barriers, are quite moving.

While Granik’s narrative films “Winter’s Bone” and “Down to the Bone” were quite bleak in tone, working in documentary has allowed her to let in a full range of emotions into the frame. The rural life she documents in “Stray Dog” looks like a hard one, with everyone just scraping by as best they can. But it’s also a loving community, where people share what they have with their friends and family. Hall is an embodiment of that spirit of generosity as much of American masculinity, and “Stray Dog” is a moving and even inspirational portrait.