How to create content automatically when a post is published?

You can use the transition_post_status action to manipulate the post content at the time when it is published. You just need to add a function like the one below into your theme or plugin:

function post_published( $new_status, $old_status, $post ) {
    if ( $new_status == 'publish' && $old_status != $new_status) {
        //Do whatever you want to the post
    }
}
add_action( 'transition_post_status', 'post_published', 10, 3 );

In this function, $post is a WP_POST object, so you can use it to manipulate the post in all kinds of ways. Adding a string to the top of the content would be a simple as this:

$newcontent="the content you generated";
$post->post_content = $newcontent . $post->post_content;

I am not sure what you want DISPLAY OF CONTENT to be. If you just want to display the post meta in some original way, then just editing your template file would be much simpler.

Check out these Codex pages for more info:

WP_Post

Post Status Transitions