In this pattern, it has no meaning. It is used only to fill the subject position in the sentence. Thus, it is called introductory “it”. Introductory “it” can fill the position both of the subject and object. Introductory “it” as a subject:
To watch musical programs is pleasant. IT IS PLEASANT TO WATCH MUSICAL PROGRAM.
To play football must be fun. IT IS FUN TO PLAY FOOTBALL.
INTRODUCTORY “IT”
Introductory “it” can fill the position both of the subject and object.
Introductory “it” as a subject:
To watch musical programs is pleasant.
IT IS PLEASANT TO WATCH MUSICAL PROGRAM.
To play football must be fun.
IT IS FUN TO PLAY FOOTBALL.