Anybody with a name like Viper must be one bad dude.
Commander Mike "Viper" Metcalf fits the bill. He's the head honcho at Top Gun, and he was the first guy to win the coveted Top Gun trophy. He's your typical, no nonsense, high-ranking naval aviator. Viper didn't get that far up the food chain without making a name for himself, and the implication is that he made that name during the Vietnam War, where he flew with Maverick's father.
Pushing the Right Buttons
Now Viper knows what it takes to be an A-list fighter pilot, and he knows just which buttons to push, especially when it comes to Maverick. He sees shades of Duke Mitchell (Maverick's father) in Maverick, and tells him so near the end of the film:
VIPER: You're a lot like he [Maverick's father Duke], only better. And worse.
Viper's past history with the Mitchell family means he knows how to get through to Maverick, which is why Maverick ultimately decides to not quit Top Gun, and the Navy. Viper tells him about his father (which could get Viper in a lot of trouble as what he tells him is classified), and he knows that this is what Maverick needs to hear.
Part of the reason Viper is a good commander, a good pilot, and a good instructor is that he doesn't sugarcoat anything. He's gruff and blunt. That's the way to get through the Navy pilots.
For example, during the first Top Gun session he says flat out:
VIPER:This school is about combat. There are no points for second place.
Later, while disciplining Maverick and Goose he tells them that if they don't obey the rules, they'll be "history." Plain and simple.