The leader of this group is Mike.问谁是主语

主语:the leader

the leader of this group 是主语

the leader of this group是主语
is 是谓语
Mike是宾语

Mike.

The leader of this group is Mike.
The leader是主语.
of this group 是定语修释主语.
主语+is Mike是主系表结构.

the leader of this group 整个短语是主语