Run function if most recent post outside loop?

Just to clarify the above is on my post page and the function is basically at the bottom of the page outside of the if (have_posts()) loop.

My understanding is i cant use $posts[0] == $post outside of the loop?

So would i use something like
<?php
$firstpost = get_posts( ‘numberposts=1&post_date&order=DESC’ );

if $firstpost = 1;
echo display_message();
else;
/* do nothing */
endif
?>

Or something like

$getlatestpost = get_posts(‘numberposts=1&order=DESC&orderby=post_date’);
$latestpostid = $getlatestpost ->ID;

If $post->ID == $latestpostid;
echo display_message();
else;
/* do nothing */
endif;

Would that work? Am I making any sense lol. I just want to run a function on my single.php at the bottom of the page if its not on the latest post.

Here’s how I got it to work for me, let me know if you have any problems adapting it:

<?php

	// query database for most recent post in category 3
	$query = get_posts('numberposts=1&category=3');
	foreach ($query as $post) {

	//set variable as title of most recent post
	$title = get_the_title();
	}

	//start new loop
	if ( have_posts() ) : while ( have_posts() ) : the_post();

	//set variable as title of current article
	$title2 = get_the_title();

	//if titles are the same, do this
	if ( $title == $title2 ) {
?>
	<h1>In This Issue</h1>
<?php

	//else if in that category and titles are not the same, do this
	} elseif ( in_category('3') && $title != $title2 ) {
?>
	<h1>Previous Features</h1>
<?php

	//else if in different category, display standard message
	} else {
?>
	<h1><?php the_category(' '); ?></h1>
<?php
	}
?>