Yes, it is possible to remotely lock your lost iPhone using the Find My app or iCloud. This feature allows you to locate, lock, and erase your device if it is lost or stolen. Here's how you can do it: 1. Sign in to iCloud.com/find on your computer or another iPhone and sign in with your Apple ID and password. 2. Click on the "All Devices" drop-down menu at the top of the screen and select the lost iPhone from the list of devices associated with your Apple ID. 3. Click on the "Actions" button (looks like a circle with a line through it) next to the selected device and choose "Loss Mode." Follow the prompts to set up a passcode for the locked device and enter a contact phone number where you can be reached. 4. Customize a message that will appear on the locked iPhone's display, such as "This phone has been lost. Please call [your phone number] if found." 5. Once you have entered all the necessary information, click on "Done" to activate Loss Mode on your lost iPhone. The device will now be locked and require the passcode you set up to unlock it. 6. If your lost iPhone is powered on and connected to Wi-Fi or cellular data, its location will be updated in real-time on the map within the Find My app or iCloud website. You can use this information to try and recover your device. 7. If you are unable to recover your lost iPhone, you can choose to erase all data from the device remotely by selecting "Erase iPhone" from the Actions menu. This will delete all personal information and restore the device to its factory settings, making it unusable without your Apple ID and password. However, keep in mind that erasing the device will remove any chance of tracking its location in the future.