Unread text messages are already shown in bold by default in the Messages app.
If the default bold font does not look obvious to you, you can try to change the font size or font style.
Do one of the following:
- To change the font size, go to Settings, tap , and then select the size you want.
- To change the font style, open the Themes app, and then tap . Choose a font type to download and apply it.
Note: The HTC Messages app may not preloaded in certain phone models.