Example of how to filter the Stripe payment method's $stripe_data variable to include metadata.

example.php

<?php //Please do not include the opening PHP tag if you already have one 

function tw_ee_stripe_meta_data( $stripe_data, $payment, $transaction, $billing_info) {
    if($transaction instanceof EE_Transaction) {
        $primary_registration = $transaction->primary_registration();
        
        if($primary_registration instanceof EE_Registration) {
            $primary_attendee = $primary_registration->attendee();

            if($primary_attendee instanceof EE_Attendee) {
                $stripe_data['metadata'] = array(
                    'name' => $primary_attendee->full_name();
                );
            }                    
        }
    }
    return $stripe_data;
}
add_filter('FHEE__EEG_Stripe_Onsite__do_direct_payment__stripe_data_array', 'tw_ee_stripe_meta_data', 10, 4);