Google's gallery of fonts provides a lot of style flexibility in Google Slides. Even more flexibility is available if you use the word art options in Google Slides. In the video embedded below I demonstrate the differences between using fonts and word art in Google Slides as well has how to customize your word art.
Learn many more features of Google Slides and ideas for use in your classroom in my online course Getting Going With GAFE. You can even earn graduate credits through the course.