(Updates throughout with details from church, moves dateline to St. Louis)
By Edward McAllister and Nick Carey
ST. LOUIS, Aug 25 (Reuters) - The body of Michael Brown lay in a black and gold casket topped with a St. Louis Cardinals baseball cap on Monday as family, supporters and activists gathered for the funeral of the black teenager killed by a white police officer.
The mood was upbeat as hundreds of people filed into the Friendly Temple Missionary Baptist Church, a modern red-brick church on Dr. Martin Luther King Drive in St. Louis. Christian pop music played by speakers suspended from the ceiling.
Brown's coffin lay at the front of the large sanctuary surrounded by photos of him as a child, graduating from school and smiling in a red and white Cardinals baseball cap like the one he was wearing when he was killed.
That cap lay atop the casket.
"There are no goodbyes for us, wherever you are you will always be in our hearts," read a sign accompanying one of the photos.
Outside, where gatherers sang the civil rights hymn "We Shall Overcome," the peaceful scene was in marked contrast to the violent protests that rocked the St. Louis suburb of Ferguson after Brown was shot to death on Aug. 9.
Brown's father made an appeal for calm on the eve of the services.
"All I want tomorrow is peace while we lay our son to rest," Michael Brown Sr. said at a rally against police violence that he led on Sunday with civil rights leader Reverend Al Sharpton.
"Please, that's all I ask," he told the crowd of hundreds, including the parents of Trayvon Martin, the Florida teenager shot dead by a neighborhood watch volunteer in 2012.
Like the Martin shooting, Brown's killing has focused attention on racial tension and relations in the United States. The Ferguson protests evoked criticism of the local police force's use of military gear and heavy-handed tactics.
Around the church, the police presence was heavy but relaxed. Authorities have braced for a possible flare-up, although clashes between protesters and police have waned significantly in recent days.
The National Guard, brought in to help quell the Ferguson unrest, has begun a gradual withdrawal.
Among the hundreds of people waiting outside the church was Travis Jackson, a 25-year-old retail store employee who said he took the day off from work to pay his respects.
"I had to be here. After all the emotions and pain of the past two weeks, this is an important moment for this community," he said.
"Today I am focused on peace for Michael Brown. Tomorrow I can think about justice," he added.
A grand jury began hearing evidence on Wednesday, a process the county prosecutor said could take until mid-October.
Also on hand for the funeral were Sharpton and civil rights leader Rev. Jesse Jackson. The White House said it was sending three presidential aides to attend the service. (Writing by Ellen Wulfhorst; Editing by Jonathan Oatis)