Changing themes in Ubuntu

Is it possible to install themes for Ubuntu, just like you would do that on x86/64 pc?

I did see a website where themes are submitted, but i didn’t know which one would work in Mate, there was a option of gtk2 and gtk3, i do not know how to apply them, and can i even apply them?

I assume there are themes that are resource heavy, i don’t want anything fancy, i would just like a little more modern look, most Linux desktop enviroments still look like they are from the 90-s.