PowerPoint can supplement your lecture by listing key concepts and terms that students should know. Your PowerPoint presentation shouldn't simply be a transcription of your lecture, but it should instead focus on important key ideas, delivered in short, succinct phrases.
A PowerPoint presentation is also good for illustrating your lecture with useful visuals. Choose visuals that support your lesson plan. For example, if it is a lesson on statistics, it could be supported with relevant charts and graphs. Or for a history lecture, it could be illustrated with artwork from the time period being discussed.
It is now possible to embed video and audio clips into PowerPoint as well. As with the visuals, this can be a useful and fun way to bring a lecture to life. A lecture on Shakespeare could include a clip of Laurence Olivier performing Hamlet, or a lecture on German history could be livened up with a piece of Bach.
In addition to supporting the key concepts of your lecture, PowerPoint is also great for making your lecture more fun and appealing. PowerPoint offers many different options for making your presentation visually appealing, such as changing the background and transitions between slides. Though you shouldn't overuse these tools and detract from your content, a few well-chosen bits of design can help keep your students' interest.
A PowerPoint-supported lecture can be effective, but like any teaching method, it shouldn't be the only one you use. Balance it with other teaching methods, such as class discussions and group work.