Why are these four unrelated heroes in a Superman film?

Were these all confirmed to appear?

^^ Ig they’re members of the JL

Why is the Justice League in a Superman film?

Ig it’s not an origin story

Mr. Terrific Or Hawkgirl I Don't Really Know Much About Metamorpho Just That He Exists And We Have Seen Green Lantern A Few Times In Tv Series And He's Had A Movie:-)

What on earth is Guy doing on this post?