That's exactly how a lightning conductor works; atmospheric charge attracts a ground charge which tends to leak from tall "pointy" things. The "pointier" they are, the more readily the charge leaks from them. Since this charge is of opposite polarity to that of the atmosphere it tends to neutralise the atmospheric charge, thus reducing the probability of a lightning strike. However, if the charge is insufficiently neutralised, a lightning conductor (or any other tall pointy object) will tend to "draw" the lightning to it. This is why trees are often struck by lightning.
Some interesting lightning facts:
1. Because the ground is not a perfect conductor, there is a substantial voltage gradient in the vicinity of a lightning strike. Large animals, such as cows can be killed by the voltage difference between their front and back legs. Moral: don't stand with your feet apart during a thunderstorm. In fact the best advice is to find an open area, crouch down and try to imitate a round barrow.
2. The rumble of thunder is caused by the time it takes the sound to reach our ears. Although the strike only lasts a very short time, we hear the ground strike first and then continue to hear the sound from successively higher altitudes.
3. There is an average current to earth of 6-8 thousand amps due to thunderstorms worldwide. If this could be harnessed it would provide gigawatts of power (enough to power a DeLorean in fact). ;o)
4. Lightning travels up as well as down. Ground traces often travel upwards to meet the main atmospheric bolt.
