This document discusses the use of modals and "unless" in conditional clauses in English. It explains that modals like "will", "would", and "would have" are used in the main clause to indicate likelihood or possibility. "Unless" is used to indicate an exception. The same verb tenses are used with "if" and "unless". Other expressions like "as long as", "only if", "provided", and "so long as" can also introduce conditional clauses. Modals can be used in both the main clause and conditional clause. Formal English allows placing the verb before "if" for certain conditional verbs like "had", "should", and "were".