It seems you want to generate proper metatags for your node pages (blogs). To generate them dynamically i propose to add to your module.module file next code with hook_entity_view function:
function your_module_entity_view(array &$build, \Drupal\Core\Entity\EntityInterface $entity, \Drupal\Core\Entity\Display\EntityViewDisplayInterface $display, $view_mode) {
if ($entity->getEntityTypeId() == 'node') {
$bundle = $entity->bundle();
switch ($bundle){
case 'blog':
$image = $entity->get('field_image');
$image_id = $image->getValue()[0]['target_id'];
$image_file = \Drupal\file\Entity\File::load($image_id);
$uri = $image_file->uri->value;
$facebook_image_url = Drupal\image\Entity\ImageStyle::load('your_facebook_style')->buildUrl($uri);
$facebook_metatag = [
'#tag' => 'meta',
'#attributes' => [
'property' => 'og:image',
'content' => $image_url$facebook_image_url,
],
];
$build['#attached']['html_head'][] = [$facebook_metatag, 'facebook_metatag'];
// the same for other social networks:
$twitter_image_url = Drupal\image\Entity\ImageStyle::load('your_twitter_style')->buildUrl($uri);
//etc
break;
}
}
}
And you get this metatag type meta property="og:image" content="http://static01.nyt.com/images/2015/02/19/arts/international/19iht-btnumbers19A/19iht-btnumbers19A-facebookJumbo-v2.jpg" Also you can add any metatag in such a manner:
$facebook_metatag = [
'#tag' => 'meta',
'#attributes' => [
'property' => 'og:title',
'content' => $your_node_title,
],
];
$build['#attached']['html_head'][] = [$facebook_metatag, 'facebook_metatag'];