Render a custom module inside an existing node
You can implement hook_node_build() in a custom module to add or alter elements when a node's content is by assembled for viewing, right before rendering.

function MODULE_node_build($node, $view_mode, $langcode) {
  // Only do something if the node is rendered on its own page, in full.
  if ($node-&gt;type == 'MODULE_type' &amp;&amp; $view_mode == 'full' &amp;&amp; node_is_page($node)) {
    $node-&gt;content['MODULE_stuff'] = array(
      // Insert render array content here
    );
  }
}


For sorting, you can add a #weight property in the element(s) added to $node-&gt;content. But a nicer solution is to implement hook_field_extra_fields(), so you can position the added element(s) using the usual Field UI.