<div class="main" *ngFor="let hero of heros">
  <div class="child"><mat-checkbox color='primary'>{{hero.name}}</mat-checkbox></div>
</div>

.main {
    width: 90%;
    list-style-type: none;
    margin: 0.5em;
    padding: 0.5em;
    display: flex;
    flex-wrap: wrap;
}

.child {
    width: 400px;
}

heros = [
    {id: 1, name: 'Superman'},
    {id: 2, name: 'Batman'},
    {id: 5, name: 'BatGirl'},
    {id: 3, name: 'Robin'},
    {id: 4, name: 'Flash'}
  ];