Classic Ideas in Fantasy and Science Fiction: First Contact

The biggie. The most important trope in science fiction...after guys in red shirts getting killed, of course. E.T., War of the Worlds, Close Encounters, Contact, Star Trek XXXIV, and on and on.

The Mote in God’s Eye, Larry Niven and Jerry Pournelle
"A Martian Odyssey," Stanley G. Weinbaum
“First Contact,” Murray Leinster
"The Helping Hand," Poul Anderson
The Martian Chronicles, Ray Bradbury
2001, A Space Odyssey, film, Stanley Kubrick and Arthur C. Clarke
Close Encounters of the Third Kind, film, Steven Spielberg
The Day the Earth Stood Still, film, 1951, Robert Wise, Harry Bates, Edmund North
ET, film, Steven Spielberg
The Man Who Fell to Earth, film, Walter Tevis, Nicolas Roeg
Solaris, Stanislaw Lem
Contact, Carl Sagan
Similarly:
A Signal From Space, Will Eisner (graphic novel)
His Master's Voice, Stanislaw Lem
The Hercules Text, Jack McDevitt