Pc case doesn't wanna open...

Solution
"I think it might have something to do with the metal thing sticking out on the left side."

That is just a loop for placing a lock on. Unless it is bent badly out of shape (doesn't look like it in the video), that isn't the problem.

Unless someone glued or soldered that door shut then it is just an issue of applying enough force. Perhaps you could elicit the help of a friend, but honestly if no modification have been made to the door it will slide off with enough force applied.

amtseung

Distinguished
I'll just leave this here...

It might be stuck shut since it's been closed for that long. You might just have to yank harder. Use both hands. If it really has been closed for that long, it might be time to give the innards a good cleaning.

As a last ditch effort, you can try using a flathead screwdriver or putty knife to gently pry at the edges of the panel to get it loose enough to pull out. Just don't pry hard enough to bend the slots and things that hold the panel on.
 

Luminary

Admirable
"I think it might have something to do with the metal thing sticking out on the left side."

That is just a loop for placing a lock on. Unless it is bent badly out of shape (doesn't look like it in the video), that isn't the problem.

Unless someone glued or soldered that door shut then it is just an issue of applying enough force. Perhaps you could elicit the help of a friend, but honestly if no modification have been made to the door it will slide off with enough force applied.
 
Solution

amtseung

Distinguished
It's probably locked shut or otherwise still bolted shut. I rewatched the video, and it looks like an enterprise built PC, which are typically put together and not intended for the end user to take apart and fiddle with for security reasons.

That metal tab sticking out the back is so people can lock it to a wall or floor with a cable lock and prevent thieves from easily stealing it. The Kensington lock hole is right next to it.