If you are looking to apply Lightroom-like "looks" or features to your MP4 files, you can use these common workarounds:

The in Lightroom is designed exclusively for photo editing; it is not a video editor. While you can import and play videos in the Library module , the Develop module will not allow you to apply the same frame-by-frame adjustments (like exposure or white balance) that you would use for a raw photo. Workarounds to "Develop" Video Features

: If your MP4 is failing to import entirely, it may be due to the codec. Use Adobe Media Encoder to re-encode the file to H.264 or use the YouTube preset.

Use the "Capture Frame" feature to create a JPEG of that frame. Edit that JPEG in the .