Despite being kind of a jerk, Iceman was proven to be right in the film, as Maverick’s reckless attitude led to unnecessary casualties.
In the film, Iceman was the rival to Tom Cruise’s Maverick, the two of them possessing near equal skill as pilots, but with entirely different composures.
Maverick was, well, a maverick who flew by his own rules, while Iceman was cool like…ice.
In the end, the two of them settle their differences and become friendly rivals.