use of sunjuntive

why is the subjunctive used here.

es importante que hable contigo

¡Hola Ken3883!

Once again, my apologies for the late response!

The subjunctive is used here because the phrase es importante que “it is important that” is an impersonal opinion that is colored by feeling, and such phrases are almost always followed by the subjunctive.

You can find a full explanation about this in Lesson 14.5: “Talking Emotions and Wishes,” under the heading “Talking About Opinions.”  

Do let me know if you still have any questions once you've had a look at the lesson!

Saludos,

Liss