The aim of this study is to examine to what extent Swedish writers, who write in English, use the modals must, have to and have got to. The hypothesis being tested argues that the core modal must is not being challenged by the emerging modals have to and have got to in this non-native variety of English. The objective of this thesis is to be accomplished by attempting to answer the following research questions: 1) What is the frequency and usage of the English modals must, have to and have got to in the material? 2) How do the frequencies in the Swedish material compare with the frequencies in the British and American corpora and to the previous studies? 3) How do the Swedish writers use the modals with regard to epistemic and deontic meaning? The study is corpus based, and the corpora used consist of Swedish newspapers in English (SWENC) and material from blogs and tweets which are written in English by Swedes (SESMC). These are compared with the press sub-corpora in BE06 (the British 2006 corpus of CQP web at Lancaster) and in AE06 (the American 2006 corpus of CQP web at Lancaster), which represent British and American native varieties of English. The method is quantitative and the results are presented after the process of normalization. The results show that must, have to and have got to are used in SWENC and SESMC although, to greatly varying degrees. The core modal must is more frequently used in the Swedish corpus than in the British and American sub-corpora. The emerging modal have to is used more frequently than must in all three corpora. The second emerging modal have got to is very seldomly used. Additionally, a qualitative examination of the modals and their meanings reveal that the writers in SWENC and SESMC use the older modal must alongside the newer have to and newest modal have got to, but with a preference for a toned-down style of language. The conclusion drawn is that the core modal must is indeed being challenged by the emerging modal have to even in the non-native variety of English.