Many successful rap songs feature memorable guest appearances. What would Jay-Z’s “Empire State of Mind” have sounded like without Alicia Keys? Or how would B.o.B’s smash hit “Airplanes” have fared without the assistance of Paramore frontwoman Hayley Williams?

The hip-hop genre is notorious for eccentric and unexpected, yet highly successful collaborations. They allow rap to stay fresh in a fashion that no other genre really embraces.

Sure, rockers Green Day and U2 collaborated to cover the Skids’ “The Saints are Coming” in 2006, but guest spots like that one are generally hard to come by.

There is, for example, no record outside of rap that could compare to Kanye West and Jay-Z’s 2011 release Watch the Throne. Not only did these two wildly popular rappers collaborate on the entire album, but they also did a full tour together in support of it.

And the results were staggering. The tour’s worldwide gross garnered more than $48 million, and the record was certified platinum by the Recording Industry Association of America a mere five weeks after its release date.

A good number of rappers attract a massive amount of attention on their own — such as Eminem. But adding an unexpected artist to elevate the song to a whole new level will almost certainly draw in even more listeners.

Rap songs, for the most part, are not known for being catchy. With Eminem, his catalogue is very emotionally charged and the verses are so rapid-fire that it is hard to remember what he is saying after one initial listen.

If Rihanna were to join forces with him, however, like she did on “Love the Way You Lie,” then listeners will have something catchier to sing along to. Accordingly, her vocals do not overpower the track, but rather provide a break from the verses, allowing listeners to appreciate them more and look forward to what will come after the chorus.

Jay-Z and West took part in something similar on Watch the Throne, even though they are rappers. The duo kept listeners on their toes throughout the album, forcing them to wonder who would sing next. This in turn created an exciting experience that generated a heavy amount of interest and even friendly debate about who contributed more to the songs.

This sentiment is equally as strong with present-day releases as well. Rapper B.o.B just announced the track listing Monday for his sophomore release, Strange Clouds, due in stores May 1, which includes a motley assortment of guest vocals.

Among the artists featured on Strange Clouds are T.I., Chris Brown, Trey Songz, Lil Wayne, Nicki Minaj, Taylor Swift and Morgan Freeman. Without having heard a single note, you cannot deny the fact that these guest spots are intriguing, especially the last two.

As a country-pop star, Swift is certainly not the first person that comes to mind when considering possible collaborations for B.o.B. But the biggest, most glaring and bewildering collaboration is with actor Morgan Freeman on the song “Bombs Away.”

“Bombs Away” is the opening track on the album and it is already generating a large wave of speculation as to what role Freeman will actually play. For now, all fans can do is guess because no further clues have been revealed about the alliance.

Meanwhile, the album’s first single, “Strange Clouds,” was released Sept. 27, 2011, and featured a guest appearance from rapper heavyweight Lil Wayne.

Lil Wayne’s verse comes right after the first chorus and provides a nice change of pace while adding an extra punch of star power to the track. But if B.o.B had not enlisted Lil Wayne, it is hard to imagine the track being anywhere near as effective.

In essence, guest spots on rap albums are beneficial because they bring out the best in artists. B.o.B is an excellent and innovative rapper on his own, but with icon Lil Wayne rapping alongside, B.o.B steps up his game.

Collaboration challenges these artists to work with each other to try to outdo themselves, and the results often leave listeners with a much more powerful piece of art than they would have had otherwise.

All of this is not to say that every rap song needs to be collaborative. There is enough talent in the genre for one man or woman to create an influential solo work.

But commercial success and acclaim are much easier to come by if rappers amp up their firepower with collaborations. After all, two heads are better than one, especially when they creatively figure out a way to share the spotlight.

Nick Mindicino is a sophomore majoring in print and digital journalism. His column “Industry Ballads” runs Fridays.