you should use liquid in your product page to show product size chart metafield.
To link a product and its metafield in a product page using Liquid in Shopify, your can refer below code and paste them into your
main-product.liquid
{% assign specificMetafield = product.metafields.namespace.key %}
{% if specificMetafield %}
Specific Metafield Value: {{ specificMetafield }}
{% endif %}