Metaobjects is a new feature of Shopify, introduced in latest Shopify updates.
Metaobjects configuration and data are not automatically created by the Shopify app yet. So you must manually configure fields and create data in Shopify!
Don’t worry though setting up a metaobject is not complicated. In Webflow you have just to create a CMS Collection which slug starts with metaobject-. For example, if you want to have an Events metaobject collection, you just have to create a CMS collection in Webflow in this way:
While in Shopify you have to create a new metaobject from Settings > Custom Data > Create Metaobject, and the name just needs to be event in this case
You will have to add fields for the metaobject using the same name you used in Webflow
Be sure to check Storefront and Web pages in the metaobject configuration!