Update product metafield with metaobject entry through Shopify flow

What’s the exact format for Value to get this to work? I’m Trying to update the material meta field which is a list of meta objects. I’ve tried this for the value but it gives an error. ‘gid://shopify/TaxonomyValue/1637’:

{%- for tags_item in product.tags -%}
{%- if tags_item contains “Aluminum” -%}
gid://shopify/TaxonomyValue/1637
{%- endif -%}
{%- endfor -%}

The error message is:

Exception: Got error updating metafield: “Value is invalid JSON: unexpected token at ‘gid://shopify/TaxonomyValue/1637’.” For value: “gid://shopify/TaxonomyValue/1637”, Type: list.metaobject_reference

I also tried ["gid://shopify/TaxonomyValue/1637"] and got the error “Exception: Got error updating metafield: “Value require that you select a metaobject.” For value: “[“gid://shopify/TaxonomyValue/1637”]”, Type: list.metaobject_reference”.