Avengers (Vol. I) #5
The Invasion of the Lava Men!
The Avengers are called to investigate a giant, mountainous rock that has
emerged near a military base, under the command of General Thunderbolt Ross.
Subterraneans beings called Lava Men want to use this huge, explosive boulder
to conquer the surface world. If this wasn't enough, the Hulk was last seen
in the neighborhood...
Here we can admire the greatest fighting team as they will be characterized in this roster, with excellent interactions (though Thor seems a bit grim). This will be the last appearance of the Hulk for a while in the title. Once again, he unwittingly saves the day. The Lava Men are not as impressive, but this issue is important for one reason: the enormous respect the five teammates now have for each other. Rick Jones is now the unofficial partner of Captain America. At the end, there's a direct lead-in to the next issue.
Another part of the fun is watching how various members' weakness are depicted
without shame in the story: Iron Man's failing repulsors or Thor being turned
into his alter-ego Don Blake and unable to help his comrades. Curious to
see Tony Stark, a guy suffering from a severe heart condition, calmly smoking
a cigarette!