ngmodel on mat select code example
Example: [(ngModel)] in a select
<select name="miselect" [(ngModel)]="seleccionados" multiple="multiple">
<option [value]="item" *ngFor="let item of lista">{{item}}</option>
</select>
<select name="miselect" [(ngModel)]="seleccionados" multiple="multiple">
<option [value]="item" *ngFor="let item of lista">{{item}}</option>
</select>