Knp Menu Bundle with the Metronic Admin Theme 4 sidebar menu http://bit.ly/2bfd2JS Couldn't have done it without this earlier, successful, attempt for Twitter Bootstrap: https://gist.github.com/nateevans/9958390. Rendered example: http://imgur.com/a/9LfZq If you are going to use this, make sure you have a valid license for the template!

base.html.twig

<div class="page-sidebar navbar-collapse collapse">
    <!-- BEGIN SIDEBAR MENU -->
    {{ knp_menu_render('main', {
        'currentClass': 'active open',
        'ancestorClass': 'active open'
    }) }}
    <!-- END SIDEBAR MENU -->
</div>

config.yml

# KnpMenuBundle configuration parameters.
knp_menu:
    # use "twig: false" to disable the Twig extension and the TwigRenderer
    twig:
        # Use custom template by default.
        template: :Menu:knp_menu.html.twig
    #  if true, enables the helper for PHP templates
    templating: false
    # the renderer to use, list is also available by default
    default_renderer: twig

menu.html.twig

{#
    Metronic Admin Theme 4 sidebar menu template.
    Many thanks to Niels Mouthaan for a version for generic twitter bootstrap
    Thanks to Nate Evans for posting Niels' solution on GitHub.
    Thanks to KnpMenuBundle team for their documentation.
    URL: https://gist.github.com/nateevans/9958390

    Niels' version altered by W. Sanders to make it compatible with Metronic template.
#}

{% extends 'knp_menu.html.twig' %}

{% block item %}
    {# Make some functionality of bundle available within this block. #}
    {% import "knp_menu.html.twig" as macros %}

    {% if item.displayed %}
        {# Fetch all attributes of the item. #}
        {%- set attributes = item.attributes %}

        {# Determine if item is a dropdown one with a sub menu. #}
        {%- set is_dropdown = item.attribute('dropdown')|default(false) %}

        {# Determine if item is a small, intermediate, heading to separate multiple menu sections. #}
        {%- set is_heading = item.attribute('heading')|default(false) %}

        {# Unset the checkmarks we've used above. #}
        {%- set attributes = attributes|merge({'dropdown': null, 'heading': null }) %}

        {# Set custom classes and/or automatic ones from the bundle (like first and last) #}
        {%- set classes = item.attribute('class') is not empty ? [item.attribute('class')] : [] %}
        {%- if matcher.isCurrent(item) %}
            {%- set classes = classes|merge([options.currentClass]) %}
        {%- elseif matcher.isAncestor(item, options.depth) %}
            {%- set classes = classes|merge([options.ancestorClass]) %}
        {%- endif %}
        {%- if item.actsLikeFirst %}
            {%- set classes = classes|merge([options.firstClass]) %}
        {%- endif %}
        {%- if item.actsLikeLast %}
            {%- set classes = classes|merge([options.lastClass]) %}
        {%- endif %}

        {# Build classes of the child <ul></ul> element #}
        {%- set childrenClasses = item.childrenAttribute('class') is not empty ? [item.childrenAttribute('class')] : [] %}
        {%- set childrenClasses = childrenClasses|merge(['menu_level_' ~ item.level, 'sub-menu']) %}

        {# Add one (or more) specific class(es) for correctly rendering a dropdown menu. #}
        {%- if is_dropdown %}
            {%- set classes = classes|merge(['nav-item']) %}
        {%- endif %}

        {# Add one (or more) specific class(es) for correctly rendering an intermediate menu heading. #}
        {%- if is_heading %}
            {%- set classes = classes|merge(['heading']) %}
        {% endif %}

        {# Melt all the classes together. #}
        {%- if classes is not empty %}
            {%- set attributes = attributes|merge({'class': classes|join(' ')}) %}
        {%- endif %}
        {%- set listAttributes = item.childrenAttributes|merge({'class': childrenClasses|join(' ') }) %}

        {# Put the item on display. #}
        <li{{ macros.attributes(attributes) }}>

            {%- if is_dropdown %}
                {# Render dropdown item. #}
                {{ block('dropdownElement') }}
            {%- elseif item.uri is not empty and (not item.current or options.currentAsLink) %}
                {# Render <a></a> link item. #}
                {{ block('linkElement') }}
            {%- elseif is_heading is not empty %}
                {# Render an intermediate heading for specifying sections. #}
                {{ block('smallHeading') }}
            {%- else %}
                {# Render a piece of text (no link). #}
                {{ block('spanElement') }}
            {%- endif %}

            {# Render the list of children #}
            {{ block('list') }}
        </li>
    {% endif %}
{% endblock %}

{# Renders an item with a clickable link. #}
{% block linkElement %}
    <a href="{{ item.uri }}"{{ macros.attributes(item.linkAttributes) }}>
        {% if item.attribute('icon') is not empty  %}
            <i class="{{ item.attribute('icon') }}"></i>
        {% endif %}
        <span class="title">{{ block('label') }}</span>
    </a>
{% endblock %}

{# Renders an item with text only (no link). #}
{% block spanElement %}
    <span {{ macros.attributes(item.labelAttributes) }}>
        {% if item.attribute('icon') is not empty  %}
            <i class="{{ item.attribute('icon') }}"></i>
        {% endif %}
        <span class="title">{{ block('label') }}</span>
	</span>
{% endblock %}

{# Renders the dropdown item (which has children). #}
{% block dropdownElement %}

    {# Set a break condition to exit the loop ASAP. #}
    {%- set break = 0 %}
    {# Set a variable which will determine the position of the arrow icon. #}
    {%- set unfoldedIcon = false %}
    {# Loop as long as the break is 0. #}
    {% for attrGroup in attributes if break == 0 %}
        {# If we've found the open class... #}
        {% if 'open' in attrGroup %}
            {%- set unfoldedIcon = true %}
            {%- set break = 1 %}
        {% endif %}
    {% endfor %}

    {# Add custom classes as perhaps defined within the built menu item. #}
    {%- set classes = item.linkAttribute('class') is not empty ? [item.linkAttribute('class')] : [] %}
    {# Make sure these two mandatory classes are molded in there as well. #}
    {%- set classes = classes|merge(['nav-link','nav-toggle']) %}
    {# Reset the attributes variable to the current item's link attributes (<a> tag). #}
    {%- set attributes = item.linkAttributes %}
    {# Mold all the classes in between the other attributes (separated by a space). #}
    {%- set attributes = attributes|merge({'class': classes|join(' ')}) %}

    {# Now, build the damn thing! #}
    <a href="javascript:;"{{ macros.attributes(attributes) }}>
        {% if item.attribute('icon') is not empty  %}
            <i class="{{ item.attribute('icon') }}"></i>
        {% endif %}
        <span class="title">{{ block('label') }}</span>
        <span class="arrow nav-toggle {% if unfoldedIcon %}open{% endif %}"></span>
    </a>
{% endblock %}

{# Renders the contents of the small menu sub-heading. #}
{% block smallHeading %}
    <h3 class="uppercase">{{ block('label') }}</h3>
{% endblock %}

{# Enable translation on menu items. #}
{% block label %}{{ item.label|trans }}{% endblock %}

MenuBuilder.php

<?php

namespace AppBundle\Menu;

use Knp\Menu\FactoryInterface;

/* Please note, this is a test with made up items */
class MenuBuilder {

    private $factory;

    /**
     * @param FactoryInterface $factory
     *
     * Add any other dependency you need
     */
    public function __construct(FactoryInterface $factory) {

        $this->factory = $factory;
    }

    /**
     * Builds the main menu.
     *
     * @param array $options
     *
     * @return \Knp\Menu\ItemInterface The complete menu.
     */
    public function createMainMenu(array $options) {

        // Create root <ul> node and add a few attributes to that.
        $menu = $this->factory->createItem('root', array(
            'childrenAttributes'    => array(
                'class'                 => 'page-sidebar-menu',
                'data-keep-expanded'    => 'false',
                'data-auto-scroll'      => 'false',
                'data-slide-speed'      => '100',
            ),
        ));

        $menu->addChild('Dashboard', array(
            'route'         => 'app_dashboard',
            'attributes'    => array(
                'icon'  => 'icon-home',
            )
        ));

        $menu->addChild('Demo heading', array(
            'attributes'    => array(
                'heading'   => true,
            ),
        ));

        // create another menu item
        $menu->addChild('About Me', array(
            'attributes'    => array(
                'dropdown'  => true,
                'icon'  => 'icon-user',
            ),
        ));

        // you can also add sub level's to your menu's as follows
        $menu['About Me']->addChild('Edit profile', array(
            'uri' => 'http://edit.me',
            'attributes'    => [
                'icon'  => 'fa fa-car',
                'dropdown'  => true,
            ]
        ));
        $menu['About Me']->addChild('Set Password', array(
            'uri'   => 'http://pass.me',
        ));

#        $menu['About Me']['Edit profile']->setCurrent(true);
#        $menu['Dashboard']->setCurrent(false);

        $menu['About Me']['Edit profile']->addChild('Stairs 2', [
            'attributes'    => [
                'dropdown'  => true,
            ],
        ]);


        // access services from the container!
        //$em = $this->container->get('doctrine')->getManager();

        // findMostRecent and Blog are just imaginary examples
        //$blog = $em->getRepository('AppBundle:Blog')->findMostRecent();

        //$menu->addChild('Latest Blog Post', array(
        //    'route' => 'blog_show',
        //    'routeParameters' => array('id' => $blog->getId())
        //));

        // ... add more children

        return $menu;
    }
}

services.xml

<?xml version="1.0" ?>

<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">
    <services>
        <service id="app.menu_builder" class="AppBundle\Menu\MenuBuilder">
            <tag name="knp_menu.menu_builder" method="createMainMenu" alias="main"/>
            <argument type="service" id="knp_menu.factory"/>
        </service>
    </services>
</container>