Use Quick Look. Simply press Space to instantly preview almost any file you’ve highlighted in Finder. You can use the arrow keys to move to the next file in the finder window below. For multiple files selected you get a film strip in Quick Look.

Lots of extra options are surfaced in MacOS when Option is held. Press option while any menu is open and you’ll see new options. The context menu will show that quick look becomes full screen preview in this case. Lo and behold simply pressing Option Space will do the same thing.