1 

Make a new file in photoshop, about 500X200. Select the gradient tool, click
once on the gradient that shows up at the top to edit the gradient. Click once
in the middle of the gradient to set a new gradient point, select white color for
it and make the ones on the right and the left black. Try to make it look like
the one above as similar as possible. After you're done editing the gradient,
enter "Metal" for the name, and click Save so you can use it in the future.

2 

Select the rectangular marquee tool and draw a big rectangle across your layer as shown.
Now using your custom gradient tool drag from top to bottom, exactly as shown above. (note:
it's important that you start and finish dragging just a little outside the selection edges).

Here is what your navbar should look like so far.

4 

Make a new layer. Now make another selection at the top of your navbar as shown above.
Then use your gradient and drag exactly as shown above to fill it up.

5 

Make another layer. Make a rectangular selection once again, this will be your button.
Using your gradient again, drag exactly as shown for the effect to be correct.