I have in my birth chart Mercury, Venus and Mars in Leo. What does it really mean?

I would think that having a lone Sun in Virgo with Mercury, Venus and Mars in Leo, you'll probably identify much more with Leo. *Triple Leo*

With Mercury you'll like to think BIG, petty minded people may get on your nerves - Mars you may make a mountain out of a mole hill or at least be dramatic when you're asserting yourself. Then Venus in Leo on top of it all, you just LOVE being smothered with attention.

Blend it all and you'd most likely have an organized showperson! If you're involved in the entertainment industry you could be the showman or the perfect assistant to one with great ideas to offer up.