Iam new to Angular JS. I am writing a login form. the requirement is show a custom message when the user clicks the submit button and the username field is blank. 

```
      <md-input-container>
            <label>{{::vm.labels.username}}</label>
            <input ng-model="vm.oLoginData.sUsername" **required**>
        </md-input-container>
        <md-input-container>

```

Everything is fine on click of the submit button i get the pop up on the filed " please fill out this field". My question is is there a way to customize the message? If so How. Any help will be much appriciated