Override of the *Flag Message* [`MessageAction`](/reactnative/object-types/message-action) shown when a user long presses a message.
The `flagMessage` function receives as a parameter the relevant message and must return a `MessageAction`.
Please refer to [the guide on customizing message actions](../../../../guides/message_actions_customization.mdx) for details.

| Type |
| - |
| function \| null |

| Parameter | Description |
| - | - |
| message	| message the action is called on |