I have an iMac and I have some mp4 videos in it. I'd like to play it from my iPad Pro remotely. Is it possible?
If you want to leave the videos on the iMac but display it on the iPad, you could put them into iTunes on the iMac and then turn on Home Sharing on the iMac. This will allow iTunes to make your iTunes library available to any Apple device on your home network. (The videos will be in "Home Videos" in iTunes. In iOS 10.2, you use the TV app to play iTunes video content.) You must also be signed into the same AppleID on both devices, and the iMac must be turned on.
If you don't want to (or can't) use iTunes, Plex can do something similar. Plex offers many additional features, but it is also more complicated to set up.