A participant in a Twilio Video call can share video and audio content, such as an mp4 or webm file, with other participants. This is achieved by creating a <video> element loaded with the intended video file, capturing its stream using HTMLMediaElement.captureStream(), publishing the video and audio tracks to the video room, and playing the file within the video element. The application needs to decide when to stop sharing content from the file, such as when playback ends or when the user stops playback manually. A working example is provided in a Twilio Serverless project that can be cloned and run locally, allowing users to test video playback with external participants.