Brief comment on modality in English

In functional grammar,modality is not only limited to traditional modal verbs.It can also be expressed in other forms.According to functional grammar theory,the problems should be studied,such as modal space,types of modality,modal commitment,modal responsibility and modalisation of certain verbs,broadening the ways of expressing modality.The purpose is to make readers know more about modality in English,identifying objective laws of applying a language properly.