You can send multiple pictures and videos over messages, also known as MMS (Multimedia Messaging Service).
- In either an existing conversation or new message, tap the "+" icon next to the message bar
- Tap on the one of the options to choose your media
- Tap on the Camera icon to take a new picture or video
- Tap on the Photo or Video icon to select an existing picture or video
- After you have chosen your media, tap the Arrow to send