I also wanted to load any iframe inside modal window. What I did was, Created an iframe inside Modal and passing the source of target iframe to the iframe inside the modal.
function closeModal() {_x000D_
$('#modalwindow').hide();_x000D_
var modalWindow = document.getElementById('iframeModalWindow');_x000D_
modalWindow.src = "";_x000D_
}
_x000D_
.modal {_x000D_
z-index: 3;_x000D_
display: none;_x000D_
padding-top: 5%;_x000D_
padding-left: 5%;_x000D_
position: fixed;_x000D_
left: 0;_x000D_
top: 0;_x000D_
width: 100%;_x000D_
height: 100%;_x000D_
overflow: auto;_x000D_
background-color: rgb(51, 34, 34);_x000D_
background-color: rgba(0, 0, 0, 0.4)_x000D_
}
_x000D_
<!-- Modal Window -->_x000D_
<div id="modalwindow" class="modal">_x000D_
<div class="modal-header">_x000D_
<button type="button" style="margin-left:80%" class="close" onclick=closeModal()>×</button>_x000D_
</div>_x000D_
<iframe id="iframeModalWindow" height="80%" width="80%" src="" name="iframe_modal"></iframe>_x000D_
</div>
_x000D_