If you refer to Green Grove Zone Boss, check the pattern of the metal ball he throws at you and don't panic. Sacrifice a life or two to learn the pattern. He always shoots it in your direction, so if you know that, you can predict where the spike ball will go.
The ball describes wide arcs and it can avoided really easily if you stick to one half of the screen and don't move too much. It bounces a few times and then it rolls a little.