diff --git a/composer.json b/composer.json
index a5f06bd..b182e4d 100644
--- a/composer.json
+++ b/composer.json
@@ -33,7 +33,9 @@
 	"require": {
 		"symfony/dependency-injection": "^7.1",
 		"symfony/framework-bundle": "^7.1",
-		"symfony/yaml": "^7.1"
+		"symfony/yaml": "^7.1",
+		"doctrine/doctrine-bundle": "^2.18",
+		"doctrine/orm": "^3.5"
 	},
 
 	"require-dev": {
diff --git a/config/definition.php b/config/definition.php
deleted file mode 100644
index 8c6eb92..0000000
--- a/config/definition.php
+++ /dev/null
@@ -1,18 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-use Symfony\Component\Config\Definition\Configurator\DefinitionConfigurator;
-
-/**
- * This file defines the layout of the configuration, type constraints
- * and any default argument values.
- */
-return static function (DefinitionConfigurator $definition): void {
-    $definition->rootNode()
-        ->children()
-            ->scalarNode('name')->defaultValue('Mr. NoName')->cannotBeEmpty()->end()
-        ->end()
-    ;
-};
-
diff --git a/config/services.yaml b/config/services.yaml
index 1dd317f..2dda648 100644
--- a/config/services.yaml
+++ b/config/services.yaml
@@ -2,27 +2,3 @@ services:
     _defaults:
         autowire: true
         autoconfigure: true
-
-    # Hide the fully qualified Greeting class name from public view
-    # but give the class an alias. This alias will be made public instead.
-    #
-    # Read the documentation to see why we do this:
-    # https://symfony.com/doc/current/service_container/autowiring.html#service-autowiring-alias
-    #
-    Pcm\MetadataBundle\Greeting:
-        public: false
-        alias: pcm_example.greeting
-
-
-    # Mark the alias we created as public.
-    pcm_example.greeting:
-        public: true
-        class: Pcm\MetadataBundle\Greeting
-
-
-    # If we were defining a twig extension, we'd want to add the twig.runtime tag
-    # so it loads correctly.
-    #
-    # Pcm\MetadataBundle\SomeTwigRuntime
-    #      tags:
-    #          - { name: twig.runtime }
diff --git a/src/Exception/MissingKeyException.php b/src/Exception/MissingKeyException.php
new file mode 100644
index 0000000..25529c2
--- /dev/null
+++ b/src/Exception/MissingKeyException.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pcm\MetadataBundle\Exception;
+
+final class MissingKeyException extends \RuntimeException
+{
+}
+
diff --git a/src/Greeting.php b/src/Greeting.php
deleted file mode 100644
index f491dbd..0000000
--- a/src/Greeting.php
+++ /dev/null
@@ -1,18 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Pcm\MetadataBundle;
-
-final class Greeting
-{
-    public function __construct(private string $name)
-    {
-    }
-
-    public function greetPerson(): string
-    {
-        return sprintf("Hello there %s! Hope you're well.", $this->name);
-    }
-}
-
diff --git a/src/Interface/MetadataInterface.php b/src/Interface/MetadataInterface.php
new file mode 100644
index 0000000..45cb73a
--- /dev/null
+++ b/src/Interface/MetadataInterface.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pcm\MetadataBundle\Interface;
+
+use Pcm\MetadataBundle\Exception\MissingKeyException;
+
+interface MetadataInterface
+{
+    /**
+     * Retrieve a value by it's key.
+     *
+     * @return scalar|scalar[]
+     *
+     * @throws MissingKeyException when the key is not set
+     */
+    public function get(string $key): mixed;
+
+    /**
+     * Sets a value against the given key. This overwrites
+     * any existing value.
+     *
+     * @param scalar|scalar[] $value
+     */
+    public function set(string $key, mixed $value): static;
+
+    /**
+     * Whether a key has been set on the metadata.
+     */
+    public function has(string $key): bool;
+}
+
+
+
diff --git a/src/Model/Metadata.php b/src/Model/Metadata.php
new file mode 100644
index 0000000..93c04c3
--- /dev/null
+++ b/src/Model/Metadata.php
@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pcm\MetadataBundle\Model;
+
+use App\Exception\Dto\Metadata\MissingKeyException;
+use App\Interface\Dto\MetadataInterface;
+
+/**
+ * Store scalar metadata on an entity.
+ */
+final class Metadata implements MetadataInterface
+{
+    /**
+     * @param array<string, scalar|scalar[]> &$metadata
+     */
+    public function __construct(private array &$metadata)
+    {
+    }
+
+    public function get(string $key): mixed
+    {
+        if (!$this->has($key)) {
+            throw new MissingKeyException($key);
+        }
+
+        return $this->metadata[$key];
+    }
+
+    public function set(string $key, mixed $value): static
+    {
+        $this->metadata[$key] = $value;
+
+        return $this;
+    }
+
+    public function has(string $key): bool
+    {
+        return array_key_exists($key, $this->metadata);
+    }
+}
+
diff --git a/src/PcmMetadataBundle.php b/src/PcmMetadataBundle.php
index 99ffdf6..b03d868 100644
--- a/src/PcmMetadataBundle.php
+++ b/src/PcmMetadataBundle.php
@@ -4,9 +4,6 @@ declare(strict_types=1);
 
 namespace Pcm\MetadataBundle;
 
-use Symfony\Component\Config\Definition\Configurator\DefinitionConfigurator;
-use Symfony\Component\DependencyInjection\ContainerBuilder;
-use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
 use Symfony\Component\HttpKernel\Bundle\AbstractBundle;
 
 /**
@@ -14,37 +11,5 @@ use Symfony\Component\HttpKernel\Bundle\AbstractBundle;
  */
 final class PcmMetadataBundle extends AbstractBundle
 {
-    /**
-     * @param array<string, mixed> $config
-     */
-    public function loadExtension(array $config, ContainerConfigurator $container, ContainerBuilder $builder): void
-    {
-        /**
-         * Load the services defined in services.yaml into the container.
-         */
-        $container->import('../config/services.yaml');
-
-        /**
-         * The "$config" variable contains an array representing the
-         * configuration and it's values.
-         *
-         * We can use it to configure the service container, for example
-         * by passing in arguments to any services we have defined.
-         *
-         * (see services.yaml)
-         */
-        $container->services()
-            ->get('pcm_example.greeting')
-            ->arg('$name', $config['name'])
-        ;
-    }
-
-    public function configure(DefinitionConfigurator $definition): void
-    {
-        /**
-         * Import the config definition (see definition.php).
-         */
-        $definition->import('../config/definition.php');
-    }
 }
 
diff --git a/src/Trait/MetadataTrait.php b/src/Trait/MetadataTrait.php
new file mode 100644
index 0000000..6b609bf
--- /dev/null
+++ b/src/Trait/MetadataTrait.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pcm\MetadataBundle\Trait;
+
+use Doctrine\DBAL\Types\Types;
+use Doctrine\ORM\Mapping as ORM;
+use Pcm\MetadataBundle\Model\Metadata;
+
+trait MetadataTrait
+{
+    /**
+     * @var array<string, scalar>|array<string, scalar[]>|null $rawMetadata
+     */
+    #[ORM\Column(type: Types::JSON, nullable: true, name: 'metadata')]
+    private ?array $rawMetadata = [];
+
+    public Metadata $metadata {
+        get {
+            $this->rawMetadata ??= [];
+
+            return new Metadata($this->rawMetadata);
+        }
+    }
+}
+