iPhone 4S only shows 1000 out of 4000 songs from iTunes, all the other titles are greyed out.

Recently converted from Android to iPhone 4S so I can have my iTunes library on my phone. I sync'd by tethering the iPhone, it went through all the steps but only 1/4 of the songs are able to play from my iPhone. All the other songs are greyed out. My iTunes library on laptop is fine, my iPod sync's the complete library and there is no problem there....only with my iPhone. I don't want to carry my iPod AND iPhone, I want my iPhone to BE my iPod! Help please...!