This is one of the more specific combinations in a chart: a house that governs self, run with Libra's instincts.
The 1st House represents self, appearance and first impressions in the birth chart. It is one of the twelve sectors of the sky at your birth, each governing a different area of life.
Its recurring themes: The core themes of the 1st House are self, appearance and first impressions. Any planet here brings its energy into this exact area of your daily experience.
Libra is a air sign ruled by Venus, known for its bold, unmistakable energy. People born under Libra are driven by cardinal momentum — they start things with enthusiasm and live with visible purpose.
In the first house, those instincts get applied to self rather than to personality in general.
Keep reading: the 1st house · Libra · Libra traits · all twelve houses · astrology guides
Yes — every house cusp falls in a sign. Which sign depends on your exact birth time and location.
No. The sign on the cusp describes the style; planets inside the house describe what is actually happening there. Both matter.
It is a background influence. You notice it most when self becomes the main thing you are dealing with.