wordpress custom field output after the_content

What I want to do is output a custom field content (which is a button with a dynamic link that's being inserted in the value of the custom field of each posts) right after the_content and before the plugins.

This is the code for the custom field:

<div class="button">
   <a href="<?php echo get_post_meta($post->ID, 'Button', true); ?>">
     <img src="<?php echo get_template_directory_uri() . '/images/button.png'; ?>" alt="link" />
   </a>
 </div>
 

On wordpress codex I also found this example of how to apply a filter to the_content in order to obtain something similar to what I want. This is the code:

add_filter( 'the_content', 'my_the_content_filter', 20 );
 function my_the_content_filter( $content ) {
 if ( is_single() )
     // Add image to the beginning of each page
     $content = sprintf(
         '<img class="post-icon" src="%s/images/post_icon.png" alt="Post icon" title=""/>%s',
         get_bloginfo( 'stylesheet_directory' ),
         $content
     );
 // Returns the content.
 return $content;
 }
 

The problem is I don't know PHP and I have no idea how am I supposed to edit the above code to apply on my specific case.

I modified it a bit and I manage to list the button, but only before the_content and without the PHP that enables the custom field.

add_filter( 'the_content', 'my_the_content_filter', 20 );
 function my_the_content_filter( $content ) {
 
 if ( is_single() )
     // Add button to the end of each page
     $content = sprintf(
         '<img class="button-link" src="%s/images/button.png" alt="Link" title=""/>%s',
         get_bloginfo( 'stylesheet_directory' ),
         $content
     );
 // Returns the content.
 return $content;
 }
 

You can see the output here: http://digitalmediaboard.com/?p=6583 (it's the top-right 'show-me' button)

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