The singer, 29, halted several times and wiped away tears as she performed the poignant Grammy-winning track, dedicated the night of the event to the animals affected by the tornadoes.
Lambert was introduced by her husband, Blake Shelton, who called her "an amazing woman, a compassionate human being, a great talent – and oh, by the way, an amazing wife."
Shelton, a native of Ada, Okla., organized the benefit for the victims of the May 20 tornado in the Oklahoma City suburb of Moore, which left 24 people dead.
He performed a duet with Usher at the concert. Darius Rucker, Vince Gill, Rascal Flatts, Reba McEntire and Luke Bryan were among the other performers, and taped messages were sent in by even more singers including Carrie Underwood, Garth Brooks, Trisha Yearwood and Alicia Keys.