This scientific research article deals with the realization and functional use of modality in Marhata Sinamot (MS) events. Due to the limited amount of time and fund, there were three MS events recorded and used as the source of data in this research. The languages used in these MS events characteristically belong to three distinctive regional dialects called Samosir, Toba, and Humbang. The types of modality in each MS events were all identified, tabulated, and used as data in this research. The data analysis was carried out by using SFL theory (Halliday and Matthiessen (2014) and the flow model of the qualitative data analysis theory (Miles and Huberman, 1984). It was found out that modality in each MS event was realized by modal, mood adjunct, and comment adjunct; and a specific realization of modality was functionally used either to express the concept of pure probability, dynamic probability, intentional probability, usuality, or obligation. The variants of modality in each MS events characteristically vary from those in the others.