An introduction is a form of ceremonial speech. The mood or tone of the speech is important because we usually listen to several speeches in one class session, and the mood often changes, from serious to humorous, for example.
Introductions help the audience shift gears from speech to speech.
Indicate topic without giving away too much of the speaker's message. Establish speaker's image and set appropriate tone for the speech. Be warm, sincere, and gracious in your manner of presentation. Give your introduction in about thirty seconds to a minute.