将值从一个表复制到另一个表

I am using mysql and during an insertion to Table A, I want to also insert some values to Table B. I tried using triggers, but I don't know how to make it work the way I want it to.

Say, I have a table set as products, and it has a field product_id. I have another table, products_metadata, which also has a field a product_id.

I want to be able insert into product_metadata before an insert into products, and I want to set products_metadata.product_id = products.product_id;

I thought triggers was the way to do it, but how do I do it?