Edit in JSFiddle

JavaScript
HTML
CSS
Result

var metros;

function initialize()
{
    var map = new google.maps.Map(document.getElementById("map"),
    {
        zoom: 4,
        center: new google.maps.LatLng(22.7964, 79.8456),
        mapTypeId: google.maps.MapTypeId.HYBRID
    });

    var coords =
    [
        new google.maps.LatLng(18.979026,72.949219), //Mumbai
        new google.maps.LatLng(28.613459,77.255859), //Delhi
        new google.maps.LatLng(22.512557,88.417969), //Kolkata
        new google.maps.LatLng(12.940322,77.607422), //Bengaluru
    ];

    metros = new google.maps.Polygon(
    {
        paths: coords,
        strokeColor: "#0000FF",
        strokeOpacity: 0.8,
        strokeWeight: 2,
        fillColor: "#0000FF",
        fillOpacity: 0.26
    });

    metros.setMap(map);
}

<html>
<head>
<title>Google Maps API v3 : Hardcoded Polygon</title>
<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script>
<script type="text/javascript">
</script>
</head>
<body onload="initialize()">
<div id="map" style="width: 530px; height: 228px">
</div>
</body>
</html>