Are metadata columns required to get declared in the table's schema?

[Jie Han]

Hi community, I want to query a metadata column from my table t. Do I need to 
declare it in the table schema explicitly? 

In spark, metadata columns are hidden columns, which means we don’t need to 
declare it in the table ddl, we only explicitly reference it in our query. For 
instance, select *, _metadata from t.