A child on a white horse in front of a wall of sunflowers, the sun full on. If the Moon left only outlines, the Sun leaves nowhere to keep anything.
The Sun usually means it goes well. It is one of the few plainly good cards in the deck — results land, misunderstandings clear, the ambiguous becomes definite. There is no need to read it cleverly.
The quality of the good is worth noting though. The rider is a child, and that is not incidental. The joy here is simplicity rather than achievement — not the relief of a long effort finally paying, but the ease of having nothing to hide. If something you are concealing is sitting heavy, this card also reads as: put it on the table.
Reversed, the good thing arrives flat. It worked and you do not feel it, or it is late, or it is less than you pictured. Or you assumed it would all be fine and skipped the preparation. Sun on the field does not ripen everything by itself.
The Sun gets filed as the best card and read with relief, but its core is not luck — it is having nothing to hide. Bright also means fully visible. Where something has been kept out of sight, this card is not purely welcome. Things going well and things coming to light arrive together.
With Judgement you have to decide about what has come to light. With the Devil, stepping into the light is what cuts something loose. Remember that the Sun is lighting rather than an ending and it misreads less often.