The Martians use a vast array of machines for different uses. The most familiar is the Fighting Machine. It has three legs, two red lights, two big green 'eyes' and covered in 'glittering' metal.
They are very tall as they are described in Jeff Wayne's interpretation as higher than the tallest steeple. They carry a heat ray which turns eveything to fire.
There are many different interpretations of the Fighting Machine. There is the George Pal version which looks like a 'swan' and lots of other random interpretations trying to make one like HG Wells describes them.