Modal giratório - Voltar

@keyframes animacao {
	0% {
		transform: rotate(-360deg);
		opacity: 0;
	}
	100% {
		transform: rotate(0);
		opacity: 1;
	}
}

.girar {
	animation: animacao 0.6s ease-out;
}

<!-- Modal -->
<div class="modal fade" id="myModal" tabindex="-1" aria-labelledby="exampleModalLabel" aria-hidden="true">
<div class="modal-dialog modal-dialog-centered">
	<div class="modal-content girar">
	<div class="modal-header bg-success">
		<h5 class="modal-title text-light" id="exampleModalLabel">Aviso
		<button type="button" class="close" data-dismiss="modal" aria-label="Close">
		<span aria-hidden="true">×</span>
		</button>
	</div>
	<div class="modal-body">
		Olá!!! <br>Sou um modal giratório
	</div>
	<div class="modal-footer">
		<button type="button" class="btn btn-dark btn-sm" data-dismiss="modal">Ok</button>
	</div>
	</div>
</div>
</div>