<button type="button" data-toggle="modal" data-target="#exampleModal" class="btn btn-success">Click</button>

<div class="modal" id="exampleModal">
<div class="modal-dialog">
<div class="modal-content" style="height:100px;">
 <div class="close-button">
<button type="button" class="close" data-dismiss="modal">&times;</button>
 </div>
 </div>
</div>
</div>

.close-button button {
  border: 1px solid black;
  border-radius: 50%;
  height: 25px;
  width: 25px;
  outline: none;
  }

  .close-button {
  margin-right: 50%;
  margin-top: 7%;
  /*  I wrote to center the button */
  }