Keynote (Apple) and Power point (Microsoft) are the most used programs, depending on whether you use Mac or PC, to prepare slide shows. Keynote is used more in the artistic world, among designers, and PowerPoint more in the business and home world, but the process of creating a presentation is very similar in both programs.
However, what both programs are quite weak on is their templates by default, that's why here I bring you a good compilation of 40 Slide Show Templates for Keynote and PowerPoint. Some are free and others are paid, but they are not very expensive, there are some that are worth € 3-4.
Source | 40 templates for Keynote and Power Point
I would like to see the templates