In mythology, Hermes-Mercury made a lyre-guitar for Apollo the Sun god.
In astrology, the Sun is the energy of expressing our selves, our whole selves, nothing but our authentic selves, which at some level, may be ego but the more we refine it becomes nothing but love. Great artists never show works of “me me me..” but works of “love love love..”
Mercury provides the tools. If the Sun is love, the guitar, the manual dexterity that needs to be trained through daily practice, the lungs and vocal chords to sing and the words to say are from Mercury. The painter loves and Mercury provides the paints, the brushes, the eyes to see and the skills to translate the pictures in the mind into colours on the canvas.
All artists know that you can’t just do anything directly from inspiration to realisation. A composer knows what instrument they are composing for. There are things that are possible with a trumpet but not with a guitar. The instrument, the messenger, the intermediate plays a great role and Mercury in our chart says something about how we translate inspiration into expression.
My examples are taken from arts, but Sun’s expression is not limited to arts – unless we remember that we are the artists of our own life, whatever we do with it.