Display random posts on the home page in WordPress

functions.php

<?php

add_action( 'pre_get_posts', 'display_random_posts' );
/**
 * Callback for WordPress 'pre_get_posts' action.
 * 
 * @link http://codex.wordpress.org/Plugin_API/Action_Reference/pre_get_posts
 * @author Ryan Meier <rfmeier@gmail.com>
 *
 * @param object $query The current query object
 */
function display_random_posts( $query ){
        
        // check for main query and home page
        if ( $query->is_home() && $query->is_main_query() ) {
                
                // set the order to random
                $query->set( 'orderby', 'rand' );
                
        }
        
}