While you can use iMovie or Photos to create slideshows, Keynote is probably the most advanced tool with the most options. You can quickly import many photos onto individual slides. Then you can work with each slide to scale and adjust each photo. You can add text and transitions. You can even create a Ken Burns effect by moving and scaling a photo over time. Once you have perfected your slideshow, you can export it as a video to share. You can also record naration to include in the video.