IIS Metabase is a structure where IIS configuration settings are stored. The metabase configuration and schema for IIS 4.0 and IIS 5.0 were stored in a binary file, but from IIS6.0 the configuration and setting is stored in single binary file (MetaBase.bin), with plain text, Extensible Markup Language (XML)-formatted files named MetaBase.xml and MBSchema.xml. You can navigate through the IIS Metabase using MetaEdit or Metabase Explorer.
The Metabase is based on a hierarchical design with inheritance. Each object in the metabase has a KeyType. The KeyType property specifies the type of metabase key.
Each property of an object has a set data type and can be configured at specific locations. For example, XoverTableFile can only have string value. And this property can be configured only at IIsNntpServer. You can fing the full list from MSDN.