/* Add Tag from Article to Meta Tag */
function add_tag_from_article() {
	if ( is_singular() && is_single() ) {
		global $post;
		$tags=get_the_tags( $post->ID );
		foreach ( $tags as $tag ) {
			?>
			<meta content="<?php echo $tag->name ?>" property="og:tag" />
			<?php
		}
	}
}

add_action( 'wp_head', 'add_tag_from_article' );