The keynote will feature a new "iCloud" service, the company said. It didn't explain what the service will do, but Apple has been in talks with all four major recording companies on allowing users to store their songs on Apple-run servers rather than on their home PCs, according to a person familiar with the matter.
The person was not authorized to speak publicly on the deals and spoke recently on condition of anonymity.
Jobs went on medical leave in January for unspecified reasons, handing over day-to-day control to chief operating officer Tim Cook. Investors were rattled because Jobs is seen as the creative force behind the company, crucial to shaping hit products like the iPod, iPhone and iPad.
Apple shares rose $10.42, or 3.1 percent, to close at $347.83.
Apple's annual Worldwide Developers Conference kicks off Monday in San Francisco.
Jobs decision to appear at the conference indicates he believes iCloud will be another breakthrough service for Apple.
ICloud could give users a wide array of music for their iPhones, iPads and Wi-Fi-capable iPods, without having to connect them to their home PCs to transfer songs. Google Inc. and Amazon.com Inc. have recently launched similar services.
The Wall Street Journal reported Tuesday, citing unnamed sources familiar with the matter, that iCloud would allow users to scan their home music collections and have it duplicated in the "cloud" of Apple-run computers. That would remove the time-consuming hassle of having to upload every song to the online storage locker.
Eliminating that hurdle would give iCloud a leg up over the comparable services from Google and Amazon.com, which requires uploads of existing song collections. Neither Google nor Amazon has secured deals with the recording companies.
It's unclear how Apple intends to make money from the iCloud service, although a subscription plan seems likely.
Apple's statement also said the keynote speech will feature Apple's new Mac software, Lion, and the next version of Apple's iPhone and iPad software.
The June developers' conference has in years past been the opportunity for Apple to reveal the year's new iPhone model, ahead of a retail launch a few weeks later. But this year, analysts are speculating that the new iPhone won't arrive until the fall. Apple launched a version of the iPhone 4 for Verizon's network in February, and a June-July release of a new model could disappoint new owners of that phone.
Tuesday's brief statement did not mention any new hardware.