"The Metal Master!" (X-116) by Lee and Ditko; 24 pages.
General Ross' testing of a new rocket goes disastrously, as the alien Metal Master arrives and melts the weapon to the ground. The only one who can fight him is the Hulk, and he has to use his wits to gain the upper hand. Rick Jones is tired of being a powerless sidekick, and so starts the Teen Brigade to assist in crime fighting. The Hulk is pardoned for his part in saving the world, and Bruce and Betty finally confess their love for each other.
1st appearance of the Teen Brigade and the Metal Master.
Pages 1 - 10 reprinted in Marvel Collectors' Item Classics #11.
Pages 10 - 18 reprinted in Marvel Collectors' Item Classics #12.
Pages 18 - 24 reprinted in Marvel Collectors' Item Classics #13.