Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a slow brooding drama about members of a Christian snake-handling church in Appalachia. Venomous snakes are willingly handled by church members to prove their faith and purity. If a believer handles a snake and it bites and envenomates them, it means they are not pure of sin. Snakebite victims are supposed to pray for forgiveness instead of going to a hospital for snakebite treatment. It's based on the real snake-handling churches that were founded in rural Appalachia in the early 20th century and continue today mostly in the Appalachians and the rural South in states in which handling venomous snakes in a way that can endanger others is legal.
It's a portrait of an unusual religion and an exploration of the limits of faith, but mostly it's a coming-of-age love triangle between the domineering Pastor's pregnant unmarried daughter and the two men who love her.
Most of the snake scenes are realistic, including an envenomation and its horrible consequences. We also see a group of church men on a realistic fieldherping outing, with snake hooks and collecting boxes, hunting for snakes to catch for the church. Even though one of them finds a rattlesnake covered by leaves, which is not too likely, I'm not going to complain, because it's extremely rare to see people hunting for snakes in a fiction film.
The opening scene in which Mara, the Pastor's daughter, takes a boy to see what she calls a "maternity den" of snakes lying on warm rocks to keep their bodies warm, is not too unrealistic either, since it's based on Timber Rattlesnake dens in rocky areas in the Appalachians. Female rattlesnakes do give live birth instead of laying eggs. (Though the snakes we see in the "den" are not rattlesnakes.) Apparently Timber Rattlesnakes in some areas can be found at den sites throughout the year, not just after they emerge from winter brumation (hibernation.)
The snakes we see being handled are mostly harmless species, of course, because we can't expect actors to handle live venomous snakes. In movies we have to pretend that harmless snakes are venomous. But it has always bothered me that people who watch movies with harmless snakes portraying venomous snakes are led to believe that all snakes are venomous or at least that the harmless species shown in the movie are dangerous. (Imagine that people believed that harmless little bunny rabbits are vicious killers after seeing the Killer Rabbit in Monty Python and the Holy Grail and you'll understand my complaint.) When we do see venomous rattlesnakes, they're not the right species for the area, Timber Rattlesnakes, they're Western Diamond-backed Rattlesnakes found in western North America. The harmless snakes we see are mostly gopher or bull snakes, along with rat snakes, kingsnakes, and milk snakes.
Actor/Comedian Jim Gaffigan has a small role in the movie, and much of it takes place in his house, including an arm amputation scene in which he uses a reciprocating saw. (Those things are handy to have around.) I expected to see boxes of Hot Pockets piled up in his kitchen but I must have missed them.