Lakshmi,
the component file is the main file to load all the resources needed and it has to call the init method at the start of the application. see this official documentation
https://sapui5.hana.ondemand.com/#docs/guide/4cfa60872dca462cb87148ccd0d948ee.html
keep in mind that the metadata section is only to describe the application while the init is in fact important in order for the app to work correctly.