St Mary’s Church in Ballybrack was overflowing as family, friends and the community gathered to say goodbye to the popular young man.
Many mourners had also attended the funeral Mass of Alana Harkin on Friday morning, at which Thomas was also remembered.
The two friends both sadly passed away following a road traffic collision in Gleneely in Inishowen on November 6.
Father Eddie Gallagher said that Thomas’ parents, Helen and Dominick, wanted his funeral to be a celebration of his life.
He said “Our gathering in tragic circumstances reminds us of the preciousness of human life and how things can change so drastically for us in the blink of an eye.
“In the first hour of Monday, life changed and will never be the same for Thomas and Alana’s families.”
He said that everyone at his funeral mass wanted to remember Thomas at his best.
Fr Gallagher added “He packed a lot into 18 years of life. He was looking after everyone else from the moment he was born. He was protective of you all. When he was told he was having a baby sister, he literally jumped for joy. He was so happy that his family felt so complete and he happily walked Emily around the estate in a pram.
“Thomas understood how important it is to live each day as a new gift from God. ”
Among the gifts and symbols of Thomas’ life were his Versace aftershave, his Ellesse coat, a frying pan and eggs, his working boots and clothing, a framed pictured from his formal, badge from vintage tractor and a horse-riding cap.
Also among the gifts were a hand-carved wooden heart with pictures of Thomas and Aoife, his girlfriend of 18 months.
Fr Gallagher recalled the young couple’s love of each other and also spoke of Thomas’ friends or the ‘boyos’, who were like a ‘Band of Brothers.’
As well as his football and hurling, his love of horses brought out the best in him and all the young people he helped at Cooley Equestrian Centre in Moville.
Fr Gallagher turned his attention to Thomas’ mother Helen, an art teacher at Moville Community College and to how her son wasn’t embarrassed despite his mother’s position in the school.
Mourners heard how family and friends were everything to Thomas.
There were many tears shed as a friend read a poem chosen by Thomas’ heartbroken father Dominick and during a closing song from Thomas’ classmates at Moville Community College, which was met with a ’round of applause.
Thomas was described earlier this week by the principal of Moville Community College, Caroline Doherty, as someone who had a ‘smile that could brighten any room,’.
"Thomas is described by his teachers as mature beyond his years - a real presence in the classroom. He had a fantastic sense of humour and a smile that could brighten up any room. “His kindness and personality meant that he was loved and respected by both his teachers and his peers.”
Thomas Gallagher was laid to rest following Requiem Mass.