You can better express yourself in the messages you send by formatting, styling, or animating the text in your message, the message bubble, or the entire screen.
Note: To send and receive messages with text formatting or text effects, you and your recipients must be using above the keyboard, then select your preferred style (bold, italic, underline, or strikethrough) or animated effects (big, small, shake, nod, explode, ripple, bloom, or jitter).
The Messages app may suggest effects to apply as you type.
Tap , then tap the gray dots to preview different bubble effects.
Tap on your iPhone.
In a new or existing conversation, type a message or insert a photo or Memoji.
Touch and hold Use iMessage apps in Messages on iPhone