Second in a series of “Turn Your iPhone Sideways” posts.
Depending on the model of phone you have, and whether you have Display Zoom enabled, turning the iPhone sideways may show the list of messages alongside the message you’re reading. You can tap the two-headed arrow at top to go full-screen.
Also depending on the model of iPhone you have, and whether you have Display Zoom enabled, rotating your iPhone may increase the size of the text.. The increased size can make the difference between squinting and reading comfortably. See below.