There are thousands of satellites and satellite debris in orbit around the Earth.
Artist Interpretation of a GPS satellite
Source: image courtesy of NASA
Some satellites, particularly communication satellites are in geosynchronous orbit, which means that they orbit the Earth at the same speed as the Earth rotates, so they remain fixed above one spot. These satellites are 35 700 km above Earth and are not visible with the naked eye.
Other satellites, such as weather monitoring satellites, are in low-earth orbit just 300 - 800 km above Earth. They orbit the Earth every 90 minutes. These satellites shine by reflecting light from the Sun and can be seen as bright star-like objects that move steadily across the sky. The best times to see satellites are just after sunset or before sunrise.
The Heaven's Above Satellite website includes all the details you need to catch a glimpse of the satellites passing over Melbourne including the International Space Station and the Hubble Space Telescope.