I'm trying to get an artist's number of followers.
If I use the metadata api call
http://ws.spotify.com/lookup/1/?uri=spotify:artist:4YrKBkKSVeqDamzBPWVnSJ
I just get the name of the artist.
I'm assuming you want a PHP solution.
Using the spotify-web-api-php library (shameless self promotion) it's really easy. Take a look at this example:
<?php
require_once 'src/Request.php';
require_once 'src/SpotifyWebAPI.php';
$api = new SpotifyWebAPI\SpotifyWebAPI();
$artist = $api->getArtist('0OdUWJ0sBjDrqHygGUXeCF');
echo '<b>Number of followers:</b> ' . $artist->followers->total;
As mentioned earlier, also take a look at the official Spotify docs.