Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
Bruce Lee died before this move was released, but it made him an international superstar and kicked off a martial arts movie craze. Lee plays a martial artist named Lee who is training and teaching at a Shaolin Temple in Hong Kong. The headmaster of the temple tells him that Han, a former member of the temple, has defied their beliefs and perverted all they hold sacred. He asks Lee to reclaim their lost honor. (Han is also an expert fighter who attaches a hand made of knives to his artificial hand.) A British agent tells Lee that Han is a drug dealer who addicts young women then sells them into sex slavery, but they need proof to convict him. He asks Lee to enter Han's martial arts tournament, held on his private island where no guns are allowed, and find evidence to prove Han's illegal activities. He tells Lee to try to get to the island's radio room and send a message to him, then he will send in the law to bust Han.
After Lee gets to the island, he and the other fighters are confined to their rooms for the night. Lee sneaks out anyway and discovers a ventilation shaft hidden under some potted plants with a door that he opens up and shimmies down into on a rope. But a guard discovers the rope and cuts it. Lee returns the next night, but when he moves the potted plants this time there is a venomous snake on the door. (I think we're supposed to assume that the snake was put there to guard the opening after Lee was discovered the previous night. This is ridiculous, of course, because it's very unlikely that a snake would stay in one place like that. It would make more sense to post a human guard there, but good sense often makes for a less exciting movie.) Lee is carrying his rope in a black bag. He removes the rope and puts the bag over his hand, then grabs the snake with his bagged hand, reverses the bag, and slowly pushes the snake inside. (Lee is obviously aware of the movie cliche that snakes can be used as weapons.) After Lee gets to the underground crime lair and learns what is going on there, he finds the glass-windowed radio room. He pulls the cobra out of the bag then smacks it on the head for no apparent reason other to show us how fast and fearless he is. Then he opens the door slightly and puts the cobra inside on the floor. The two men inside the radio room see the snake on the floor, panic, then smash one of the glass windows and jump out of the room while Lee watches with a bored expression - the same expression I always make during a snake scene when people are acting like fools because of a snake. Lee then goes inside the room, puts his foot on the cobra so it won't bite him, and sends a message on the telegraph.
Not only did they use a real live cobra for the scene, Bruce Lee actually handled it. I've read that the snake's venom glands were removed and that the snake actually bit Lee during one take, but he wasn't harmed. Still, it's almost unheard of for an actor to handle a real venomous snake, de-venomed or not. It adds a lot of realistic value to the scene. It would be impossible to do today because it's considered animal cruelty and because the insurance companies would not allow it.
Considering that all Lee did with the snake was catch it and release it to take advantage of the men's fear of snakes, this might be the most realistic snake-used-as-a-weapon scene in any movie. It could really have happened.