Impersonal Expressions and the Subjunctive

Impersonal Expressions used with the Subjunctive function the same way as emotions and denials work with the Subjunctive. The focus is on the subjectivity of the subject and noton the reality of the situation or event. There is a long list of adjectives we can use with Es - all of which require the Subjunctive when followed by que and a change of subject. For example:

It's important that she study every night.	Es importante que ella estudie cada noche.
It's great that he is coming to the party.	Es bueno que él venga a la fiesta.
It's probable that Keanu will eat dinner with us.	Es probable que Keanu coma la cena con nosotros.
It's marvellous that Antonio Sabáto is dating our professor.	Es maravilloso que Antonio Sabáto salga con nuestra profesora.

It doesn't matter if something is important, probable, critical, necessary, good etc. because these are value judgements and not statements of objective fact. It is your opinion of the statement rather than the statement itself which is the focus.

However, statements that state Truth (Es verdad que..., etc.), Certainty (Es cierto que...,etc.), and Fact (Es hecho que..., etc.) don't use the Subjunctive! See "When not to use the Subjunctive"