The whole hospital scene shows michael's coolness and quick alertness to emergency in protecting his father.

Once the car full of solozzo hitmen had left, enzo the baker was seen as shaking and nervous as to what had jus happened. When enzo tried lighting his cigarette he could not due to his shaking. Once michael held the lighter he noticed that his hands were perfectly still and he was not shaken to bits like enzo was.

This was the realisation that he had become sort of like his father calm and cool in emergency.

Many see this scene as the defining moment of michaels transformation from a 'college' boy to the don we see later on in the trilogy.