Add basic Open Graph Tags

<meta property="og:title" content="<?php echo esc_attr( get_the_title() ); ?>"/>

<meta property="og:description" content="<?php echo esc_attr( get_the_excerpt() ); ?>"/>

<meta property="og:url" content="<?php echo esc_attr( get_permalink() ); ?>"/>

<meta property="og:type" content="article"/>

<?php if ( has_post_thumbnail() ) : ?>

<meta property="og:image" content="<?php echo esc_attr( get_the_post_thumbnail_url() ); ?>"/>

<?php endif; ?>