How to replace merge tags of Mandrill template in drupal. after some digging i found some solution its work fine for me. but i think its require more effort and carry the merge tag to 3 step.

First step is:-

//Implementation of hook_mail()
function mymodule_mail($key, &$message, $params){
    if($key == "sendmandrillmail"){
        $message['subject'] = 'This is a test mail subject';
        $message['body'] = 'This is a test mail body';
        //provide value to marge tag.
       $message['global_merge_vars']=array(
                    array(
                                   'name' => 'FNAME',
                                   'content' => 'Dileep',
                            ),
                  array(
                                   'name' => 'LNAME',
                                   'content' => 'Maurya',
                            )
            );
    }
}

Second Step:-

/**
 * implementation of hook_mandrill_mail_alter()
 */
function mymodule_mandrill_mail_alter(&$mandrill_params, $message) {
        if(!empty($message['global_merge_vars'])){
        $mandrill_params['function'] = 'mymodule_mandrill_template_sender';
        $mandrill_params['args']['global_merge_vars']=$message['global_merge_vars'];
        }   
}

Third step :-

function mymodule_mandrill_template_sender($message, $template_id, $template_content,$global_merge_vars) {
  if ($mailer = mandrill_get_api_object()) {  
     $message['global_merge_vars']=$global_merge_vars;
    return $mailer->messages->sendTemplate($template_id, $template_content, $message);
  }
  return NULL;
}

Can i reduce this step?