This study attempts to examine the use of English modals in terms of their frequency and functions. For this purpose, Form 4 and College students' argumentative compositions were extracted from the Malaysian Corpus of Students' Argumentative Writing (MCSAW). In order to analyze the data, this study employed discourse analysis and some descriptive statistics by using the WordSmith Tools Version 4.0. The findings of the study showed that Form 4 and College students used "can" and "will" more frequently in argumentative compositions compared to other modals. Moreover, the result illustrated the exploitation of present tense form of modal than the past tense form. Finally, it was also revealed that the modals of ability were the most frequent modals found in Form 4 and College students' compositions in terms of their appropriate function. In order to improve the teaching, learning and effective usage of modal auxiliaries among ESL learners, all the central modals must be emphasized repetitively to enhance students' understanding of modals and their functions.