Keynote is often thought of as the Mac equivalent of PowerPoint and offers many of the same features. While it is primarily used by Mac users, presentations can be output as PDFs or converted to PowerPoint formats, so you can deliver your presentation virtually anywhere. Note, however, that the formatting may change some when you convert your presentation to the PowerPoint format, so it is always a best practice to review it after conversion to ensure that all of your layouts remain the same and to make any necessary tweaks.
Keynote is available for Macs and for iOS devices.
If you want to take a look at Keynote before you decide whether to use it or if you want a tutorial on how to use it, Apple offers several short videos that introduce various Keynote functions. The video below also gives an overview of the basics of Keynote that is good for someone who is just getting started.
Note: Keynote (for Mac and iOS) comes free with a new device, so students who have recently purchased a Mac or an iPad will be able to download it without paying. Also, Keynote presentations are shareable and viewable online through icloud.com (just like Google Drive). You can even create a Keynote presentation in iCloud without having to have any of the apps.