How to put button to mat-table in Angular

You need an extra column for that, for example:

displayedColumns: string[] = ['position', 'name', 'weight', 'symbol','deleteAction'];

and to use in Mat-Table:

<ng-container cdkColumnDef="deleteAction">
    <th mat-header-cell *matHeaderCellDef> Delete </th>
      <td mat-cell *matCellDef="let element"><i class="material-icons" (click)="delete(element)">delete</i>
</ng-container> 

A working StackBlitz Example

Add this button to another mat-cell.

<button class="btn btn-outline-secondary" (click)="delete()"> <i class="fas fa-trash-alt"></i></button>