Bug Life  cycle is a process of identifying the defect and subject to rectification.
Metrics means measures.(what are all the measures taken to identify the defect)

Bug Life Cycle:New : Logged the bug by TEOpen: After review it by team lead then changed it's status to open Fixed : Once dev agree with that he can change the status to fixed once fixed that issueClo...

It is document that describes the mapping or tracing of the requirements with test cases and some time with the test data to check the test coverage and also to cross verify that we are not missing any of the test cases for that particular requirement.

It is the document that maps User requirement with the test cases to check whether the functionality coverage is achieved or not.