Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is the fourth Rambo movie which began with 1982's "First Blood" and,
as of 2019, total five movies. This one has to be one of the bloodiest action movies ever made. According to IMDB the body count is 466 with an average of 2.59 killings per minute. Most of those people die from bullets that explode their heads or bombs that send their limbs flying through the air right into your face. All that violence is why most people watch Rambo movies, but I watched it to see Rambo as a snake wrangler.
Under the opening credits we see Rambo and two men with snake hooks beside a creek in Thailand, herping for cobras. Rambo finds one, grabs it by the neck and puts it in a bag. They bring it to a snake show where we see a man performing with some cobras. We learn that Rambo works for the snake show as a professional snake collector and caretaker. We see him argue with his boss, put the cobra in a cage, and throw a rat to a python for dinner. It's obvious that he's not happy with the job and his life. (I went to see one of those snake shows in Thailand, which confirms that they attract the lowest class of tourist - guys who like snakes.)
The snake wrangler job is supposed to show us how low Rambo has sunk from his glory days as a righteous vigilante mercenary killer, or whatever he was in the previous three Rambo movies. It does look like a disgusting and dangerous job, but I've met herpers who would probably consider his snake job to be their dream job.
When Rambo is ferrying some merenaries to Burma to rescue some American Good Samaritans held captive by genocidal Burmese soldiers, one of the mercenaries tells him that this action must be better than "looking at the ass end of a snake." That really gets to Rambo, so he starts ripping the throats of bad guys apart with his bare hands. He inspires the other mercenaries to action by telling them what could be a successful military recruitment slogan: "Live for nothing or die for something." Then the rain of blood, guts, and body parts begins.