The general theme of the album is that of extraterrestrials contacting earth and of moving on. The songs themselves contain samples of reports of alien sightings and crop circle designs feature prominently in the cover and liner notes. Several tracks have been staples in live concerts ever since, especially the single "Kathy's Song", which became one of the band's biggest hits, being remixed by high-profile artists such as VNV Nation and Ferry Corsten.
The album deals mainly with the modern mythology of extraterrestrial aliens and a hope that one day the truth will be revealed to us. Generally the tracks convey a feeling of alienation as well.
Stylistically the album drew criticism upon its release for its more accessible techno-focused sound on tracks such as "Eclipse" and "Kathy's Song". There are some tributes to the Commodore 64 home computer as well, hidden in the "64k" track which is based heavily on a sample of Chris Hülsbeck's Commodore 64 version of "Axel F", and the track Untitled 4 is basically just a Commodore 64 chiptune. It is also worth mentioning that since the release of Welcome To Earth, band leader Stephan Groth tattooed a crop circle pattern on his left arm.