If an InnoDB table is being accessed at all via SELECT or DML (INSERT, UPDATE, DELETE), you should rightly expect a metadata lock.
According to the MySQL Documentation on MetaData Locking (http://dev.mysql.com/doc/refman/5.6/en/metadata-locking.html):
To ensure transaction serializability, the server must not permit one session to perform a data definition language (DDL) statement on a table that is used in an uncompleted transaction in another session. The server achieves this by acquiring metadata locks on tables used within a transaction and deferring release of those locks until the transaction ends. A metadata lock on a table prevents changes to the table's structure. This locking approach has the implication that a table that is being used by a transaction within one session cannot be used in DDL statements by other sessions until the transaction ends.
SELECTs will obtain a shared metadata lock, while DML and DDL will obtain an exclusive metadata lock. So an uncommitted