RetroGaming

Playing OOT first is not necessary, you'll pick up all the relevant plot without it. However, Majora's Mask was made as a sequel to OOT, and having the knowledge of the OOT world and characters will underscore a lot of subtext in MM that you'd likely miss otherwise.

(Nearly) every character in MM is a character from OOT, but shifted one timeline over. They're the same character but they aren't the same people. Seeing what's different between the two iterations speaks just as much as seeing what is the same.