If this aspect sits in your natal chart, your personality is assembled around beauty. That doesn't mean you're conventionally good-looking — it means that beauty, harmony and pleasant surroundings aren't a luxury for you but a condition of ordinary life. An ugly room tires you faster than hard work does. You'll skip a meal sooner than agree to a row. When there's harmony around you, you come alive; when there's dissonance, you lose energy, even if you hold it together on the surface.
The Sun governs the will, that central spine that makes you yourself. Venus governs the capacity to love and to see the beautiful. When the two stand side by side, the line between 'who I am' and 'what I love' rubs away. You quite literally become the thing you find lovely. That's why people with this conjunction so often have an instinctive sense of style: they dress intuitively well, choose a pleasant flat, surround themselves with company that's easy to look at. It works without effort, as a default setting rather than a learned skill.
The reverse of that is just as plain. When 'I' and 'what I love' merge, you need a steady supply of evidence that you, too, are loved in order to feel stable. Self-worth latches onto the reactions of the people around you. If you were told as a child 'what a beautiful girl', you built part of yourself on it. If your looks were criticised instead, the wound runs deep, because what was criticised wasn't the periphery — it was the centre.
In a woman's chart this aspect amplifies femininity as a phenomenon: softness, grace, a gift for making others comfortable. In a man's chart it works in a more complicated way. A Venus fused with the Sun makes a man diplomatic, aesthetic, sometimes androgynous. That's neither good nor bad, it's simply a characteristic. Hard decisions come less easily to such a man than to one whose Sun sits with Mars or Saturn — but he can negotiate his way through places where others end up breaking things.
Laziness, under this conjunction, works not as a vice but as a side effect. Venus relaxes any planet she comes close to. When she relaxes the Sun, you lose some of your capacity to do the unpleasant thing for the sake of a distant result. The gym, the tax return, the awkward conversation — all of it gets deferred, because there's something nicer available in the moment. It doesn't follow that you're spineless. It follows that you have to learn to outwit your own Venus: tie the unpleasant task to a pleasant context, turn obligations into small rituals, make the workspace beautiful so you actually want to be there.
In relationships, you're the person others feel good beside. You know the compliment, you know the gift, you know how to set a mood. The minus is that you can end up living for that and forgetting what you want yourself. The partner gets the pleasure while you slowly dissolve. The sign that the aspect is working badly is that you've stopped knowing what you personally love, as distinct from what you love for someone else's sake. The sign it's working well is that you can say 'no' and keep people's goodwill even after the 'no'.
Professionally this aspect leads most often towards beauty, fashion, art, design, psychotherapy, negotiation and sales — anywhere that asks you to win people over and to build a harmonious environment. If the Sun is strong by sign and house, you can build something large on it. If the Sun is weak, you'll be a gifted second beside someone else's Sun. To understand your own potential, it's worth reading the aspect not in isolation but in the context of the whole chart — the house it falls in and its links to Mars, Saturn and Jupiter all change the picture.