Matthew Lappin was born in Burnie Tasmania in May 1887. He enlisted on 20 July 1915, at the age of 28 years and 2 months. At the time, he gave as his address C% Mrs Emma Connors, 105 Victoria St., East Melbourne, perhaps a boarding house. He was, by occupation, a labourer, 5' 6" tall, an average height for the time, and by faith, a Roman Catholic. Before he was accepted into the AIF, he had to have work done on his teeth. He also appears to have been illiterate, his army record showing that he signed for his service medals with a cross, rather than a signature.

Following training, Matthew Lappan was placed with A Company, 9th Reinforcements, 21st Battalion. He embarked from Melbourne on 8 February, 1916, and disembarked at Marseilles on 27 March. He was taken on strength with the 21st Battalion on 8 June, 1916. The Battalion had fought at Gallipoli, then been transferred to the Western Front, arriving in France in March 1916. IN April, they became the first Australian Battalion to commence active operations. In July, 1916, a month after Matthew Lappan joined them, they were active in the battle of Pozieres, though mainly in a supplementary role. Matthew Lappan was designated as a 'Sapper', a term derived from the French 'Sappe', meaning spadework or trench. T be a Sapper was the equivalent rank to Private, with Sappers being responsible for building and repairing roads and bridges, laying mines or clearing mines and other munitions from the battleground. 

Conditions in the trenches were a health hazard. On 30 June, Lappan fell ill with tonsillitis and was sent away from the Battalion for treatment. He rejoined on 26 August, when the 21st battalion was active in the battle of Mouquet Farm, but was taken out of action with a gunshot wound and was admitted to hospital at Rouen. His record showed an attack of mylagia on 25 November. He was discharged from hospital in December, rejoining his battalion on 10/12/1916, but was returned to hospital on 27 December. nother bout of illness, this time Trench Fever in July 1917 saw him returned to England  on the H.S. Grantually Castle for hospital care in Bulford. He presumably would have had some leave  was then brought down by V.D. and returned to hospital.

Matthew Lappan  returned to France in July, 1918, to see out the war, but not with his original Battalion.  The 21st Battalion had suffered a severe loss of men in the Hundred Days Offensive of 1918, and was ordered to disband to provide reinforcements for other battalions. The battalion refused the order ands fought one last time in the final Australian operation of the war, Montbrehain, in 5 October, 1918. Matthew Lappan, however, was transferred from the 21st Battalion to the 6th B.G.R.(Broad Gauge Railways Unit), possibly because he was not seen as well enough to serve in anther capacity). 

When the war came to an end, Matthew Lappin returned to Australia,  and was discharged from further service. In 1919, the Electoral Roll shows him was living at 45 Seacombe St., Fitzroy North, and working as a labourer. He had married Emma Wilson in 1919, and she is listed here as Emma Lappan, barmaid. He does not appear in any other Electoral Rolls, perhaps due to illiteracy and there is no other record of his movements after this entry in 1919.