The hook you’re looking for is specifically wp_head
which could look something like this:
function theme_xyz_header_metadata() {
// Post object if needed
// global $post;
// Page conditional if needed
// if( is_page() ){}
?>
<meta name="abc" content="xyz" />
<?php
}
add_action( 'wp_head', 'theme_xyz_header_metadata' );
I believe in the long run though, since WordPress is so portable, Yoast SEO is probably the most reliable, flexible bet for SEO than something you would do yourself so I would advise against this personally.