Hi everyone. I can’t leave a group message on my IPhone. There is simply no “leave a group message “ function. What should I do. Thanks

You will only see the option to leave the group if everyone in the group is using iMessage. If anyone is using SMS, you won't see the option.

You can ask the people in the group to form a new group without you. Or, you can just mute the group. From the main conversation page in Messages, put your finger on the group message and pull to the left. Tap Hide Alerts.

Glad it helped!