When the Metro 2033 was released in 2010 it contributed to raise the PC graphics bar making good use of the latest DirectX 11 rendering technologies such as depth of field and tessellation along with high resolution textures.
Metro: Last Light follows its predecessor roots by using a heavily customized version of the 4A Engine. Three years of extra work put into the engine and you can take for granted that visual effects such as lighting, which was a huge focus for 4A Games in the original Metro have been vastly improved. There's also a lot more destruction and interactivity into the environments.
Furthermore, the developer has continued to cater to loyal PC gamers who have considerably more power than console gamers at its disposal by including a richer gaming experience visually as well as a benchmark tool for measuring your system's performance.