Friends, family and strangers who were touched by the inspiring life of Zach Sobiech celebrated the Lakeland teen at his funeral service Thursday, recalling an 18-year-old who taught millions a lesson in grace.

The Pioneer Press reports the Rev. Mike Miller said "Clouds" – a hit song Sobiech penned and performed as a farewell to loved ones – allowed the Stillwater Area High School senior to "touch people who were in a very dark place."

"The way he did it was by giving them hope," Miller said. "He let them see a little bit of the power of Christ. He is the light of the world, and He draws us out of that dark place that this world can be."

Written on blue balloons outside the Church of St. Michael in Stillwater on Thursday morning were lyrics from Sobiech's catchy tune: "Up, up, up."

Sobiech died Monday after battling with bone cancer. In a poignant tribute, mourners sung "Clouds" from memory at the end of the service, the Pioneer Press reported. All proceeds from "Clouds" go directly to the Zach Sobiech Osteosarcoma Fund.

The song continues to be an Internet sensation, with well over 5 million hits on YouTube by Friday morning, and it reached No. 1 on the iTunes singles chart. Billboard magazine reports: "The song appears headed for a potentially high debut on next week's Billboard Hot 100, possibly in the top 20, fueled largely by strong sales and likely increasing streaming activity."

KARE 11 reported that Zach's fellow songwriter, Sammy Brown, at the funeral said, "He never once complained. He handled every ounce of it with grace beyond his years."