Define global custom post

I have create a custom post object with custom post metas.

Like this:

$post-custom_meta = get_post_meta();

$custom_post = $post;

Am I how to define the $custom_post object to global in master level?

Can I request any file it like single.php

global $custom_post;

the_title();

echo $custom_post-custom_meta;

or index.php

global $custom_post;

// The Loop
if ( $custom_post-have_posts() ) {
    echo 'ul';
    while ( $custom_post-have_posts() ) {
        $custom_post-the_post();
        echo 'li' . get_the_title() . '/li';
        echo $custom_post-custom_meta;
    }
    echo '/ul';
} else {
    // no posts found
}

How to set $custom_post an global and in where? (functions.php?) thx.