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 Western comedy about Bret Maverick (Mel Gibson) a professional gambler and conman and his exploits in the American Old West with a young female con artist.
When the movie opens we see Maverick on his horse with his hands tied and a noose around his neck with the end of the rope tied to the branch of a dead tree. One of the men who left him to hang wears some rattlesnake rattles as an earring. Another tells him they're leaving but it's not good for a man to be alone out there. He drops a bag full of rattlesnakes on the ground beneath Maverick and tells him "Enjoy the company." The snakes get out of the bag as the tree branch breaks and Maverick falls to the ground next to them, but for some reason, even though we see them striking, the snakes don't manage to bite him before his horse drags him away to safety.
They used a mix of live snakes and fake snakes in the scene. Most of the live snakes were filmed separately, In the shots where we see Gibson with a live snake, they might have used composite shots or some other trickery, because it would be rare to have an actor near a live rattlesnake. The live snakes look like Western Diamond-backed Rattlesnakes and maybe Red Diamond Rattlesnakes, and maybe a Mojave Rattlesnake, also.