Most Microsoft apps use the same font by default. However ... click the dialog box launcher icon in the bottom-right corner ...

For font apps accessible as a keyboard, open any text-based app. Tap the globe icon in the lower left and select the font keyboard you want to use. Choose a specific font from the list.

Your Apple device comes with several built-in system fonts in apps like Mail and Safari—just look for the Aa icon while writing an email or searching the internet, and you can change the default ...