The best alternatives to Metastream are Togetherly, FilmFinder, and Zatalogue. If these 3 options don't work for you, we've listed a few more alternatives below.
Browse Youtube and watch it together with your best buddy in perfect sync. If one person leaves the app for a while to check something else like notifications video will be paused. Both parties can forward the video and pause the video.
Zatalogue is a social media platform that connects your social circle and movie preferences. With this you could share reviews, check what your friends are watching, maintain watchlist, create catalogue of movies, refer movies to your friends and lot more.