redirect wp-login.php to another page

If you’re only concerned about login links displayed on your pages, you should be able to modify the URL by hooking the login_url filter. This won’t redirect a user that types http://MYSITE/wp-login.php directly into their browser, but it should affect the login links displayed throughout your site.

This is the example code from the login_url Codex page:

add_filter( 'login_url', 'my_login_page', 10, 2 );
function my_login_page( $login_url, $redirect ) {
  return home_url( '/my-login-page/?redirect_to=' . $redirect );
}