Good evening Ellanos,
Welcome to the Apple Support Communities!
I understand you are interested in renting movies in 4K quality from the iTunes Store. Take a look at the resource below for more information about finding and playing 4K movies. In addition to an Apple TV 4K, you would need to have a 4K television to play these movies. I've highlighted some key information here for you. Click on the links for complete details.
Find and watch movies with 4K, HDR, or Dolby Vision
To see if a movie can play in 4K on a compatible device, look for
on the product page. By default, all videos that you can buy or rent in the iTunes Store are available to play back in HD3.
Apple TV 4K, connected to a 4K-compatible television, can play 4K content. 4K video, especially with HDR10 or Dolby Vision, requires an HDMI cable compatible with these formats. Apple recommends HDMI cables that have the Compatible Dolby Vision mark as they have been tested with Apple TV 4K and a wide range of televisions. Learn more about playing 4K, HDR, and Dolby Vision content with your Apple TV.
About renting movies from the iTunes Store
Enjoy!