GlassFish v3 Prelude is a lightweight Web 2.0 development and deployment platform built on a modular OSGi-based architecture.
Developers can benefit from a dynamically extensible and embeddable platform with support for existing Java Web technologies, JRuby, and Groovy.
It includes Java EE 5 based webtier, scripting support, OSGi support, JDBC and persistence api on top of new modular kernel of Glassfish.

Metro in V3 Prelude is available as an Addon from  Update Center module in V3  Prelude

This is a preliminary guide on how to work with Metro in the current development v3  prelude builds.

Steps to install and run v3 Prelude.

1. Unzip glassfishv3-prelude.zip downloaded from here.
 This is the web distribution for v3 and does not have support for EJBs. We have partial support for JSR 109 based webapps for Prelude.

2. Run glassfishv3-prelude/bin/updatetool.bat
You get a prompt like this

The software needed for this command (updatetool.bat) is not installed.

If you choose to install Update Tool, your system will be automatically
configured to periodically check for software updates. If you would like
to configure the tool to not check for updates, you can override the
default behavior via the tool's Preferences facility.

When this tool interacts with package repositories, some system information
such as your system's IP address and operating system type and version
is sent to the repository server. For more information please see:

http://wiki.updatecenter.java.net/Wiki.jsp?page=UsageMetricsUC2

Once installation is complete you may re-run this command.

Would you like to install Update Tool now (y/n):

Type y and it downloads the necessary files

Install image: c:\prelude\glassfishv3-prelude\bin\\..
Installing pkg packages.
Installing: [pkg:/pkg@1.0.7,0-15.1269:20081008T213041Z, pkg:/python2.4-minimal@2
.4.4.0,0-15.1269:20081008T213053Z]
Installing updatetool packages.
Installing: [pkg:/updatetool@2.0.0,0-15.1269:20081008T213110Z, pkg:/wxpython2.8-
minimal@2.8.8,0-15.1269:20081008T213126Z]
Registering notifier: Successful.
Starting notifier.
Initialization complete.

This installs the UpdateCenter

3.Run glassfishv3-prelude/bin/updatetool.exe and that brings up the gui like this
click on the Available Add-ons

4. Select Metro Web Services Stack and click install
This will copy webservices.jar, jaxb.jar and jsr109-impl.jar to

glassfishv3-prelude/modules folder. 

Note :
The following are the jars which are present in prelude. This has changed from tp2 where we had webservices-rt,webservices-tools, webservices-api and jsr109-impl.jar.

jaxb.jar : This is a JAXB OSGi bundle. It contains JAXB apis, tools and runtime classes.

webservices.jar: This is a Metro OSGi bundle. It contains all apis, tools and runtime classes which are present in Metro excluding JAXB

jsr109-impl.jar: This contains implementation to support JSR 109 Webservices for JavaEE.
Currently support if for webapps.  EJB's will be supported later.

glassfishv3-prelude/bin folder contains all the scripts like wsgen, wsimport, xjc, schemagen, wscompile, wsdeploy.

5. Deploy your war like this

glassfishv3-prelude/glassfish/bin/asadmin deploy foo.war 

after starting glassfish using

glassfishv3-prelude/glassfish/bin/asadmin start-domain domain1

You can try metro samples from https://metro.dev.java.net/
Please give us feedback if this works for you .  You can file your bugs under https://glassfish.dev.java.net/issues/ category webservices and version v3.

Additional Information
Project Metro

OSGi R4 Specification

V3 Engineers Guide

V3 Build Instructions