The principal function of the sefirot is to guide all the worlds.
The sefirot are not the revelation of God's inner reality, like words or symbols that reveal the soul or its ideas, but a means of shaping and guiding existence.
They are the equivalent of a tool like an axe, which reveals nothing of the character of the person who wields it.
This tool serves his will and acts only by the power of its owner.
–Rabbi Adin Steinsaltz
From The Thirteen Petalled Rose, Chapter 13, "Patach Eliyahu-Elijah Began," by Rabbi Adin Steinsaltz