Modal bootstrap MVC 5

I'm trying to use the modal of Bootstrap , but I can not make the window open in modal form with the page style, instead it opens as a page with no style and using the whole frame of the browser.

Following page code:

@model MyApplication.ViewModels.MyViewModel


@Ajax.ActionLink("Adicionar Endereço", "Create", "Enderecos", new { area = "Geografia", id = Model.Id },
    new AjaxOptions() { 
        HttpMethod = "Get", 
        UpdateTargetId = "modalContent", 
        InsertionMode = InsertionMode.Replace, 
        OnBegin = "onBegin", 
        OnSuccess = "onSuccess", 
        OnFailure = "onFailure", 
        OnComplete = "onComplete" },
    new { id = "btnEndereco", @class = "btn btn-lg btn-info" }
)

<a href='@Url.Action("Create", "Enderecos", new { area = "Geografia", id = Model.Id})' class="btn btn-success btn-xs">Adicionar Endereço</a>

<table id="enderecosJson">
    <thead>
        <tr>
            <th>CEP</th>
            <th>Rua</th>
            <th>Numero</th>
            <th>Complemento</th>
            <th>Bairro</th>
            <th>Estado</th>
            <th>Cidade</th>
            <th></th>
            <th></th>
        </tr>
    </thead>
</table>


<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
    <div class="modal-dialog">
        <div class="modal-content" id="modalContent">
        </div>
    </div>
</div>
@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
    <script type="text/javascript">
        function onBegin() {
            //alert('begin');
        }

        function onSuccess() {
            //alert('success');
        }

        function onComplete() {
            // alert('complete');
            $('#myModal').modal('show');
        }

        function onFailure() {
            alert('fail');
        }
    </script>
}

The screen looks like this:

Can someone give me a light where I might be wrong?