Adds meta box to posts, pages and custom post types (including default ones ..attachment, menu and revisions).

meta-box-snip.php

<?php

$post_types= get_post_types('','names'); 
$posts_separated = implode(",",   $post_types);

$screens = array( 'post', 'page',  $posts_separated);
      
    foreach ($screens as $screen) {
    add_meta_box( 'styles', 'hello', 'callback_func', $screen, 'advanced', 'high');
    }

?>