What is added after the past tense of be verb (i.e. am, is, are) Is it the present participle (verb ing), the original form or the past tense? Or something else Sorry is what is added after the past tense (was, were) of the verb be

What is added after the past tense of be verb (i.e. am, is, are) Is it the present participle (verb ing), the original form or the past tense? Or something else Sorry is what is added after the past tense (was, were) of the verb be

Was, were + present participle
Was, were + past participle --- passive voice (past tense)
Was, were + (about) to + verb prototype --- past future tense
Was, were + going to + verb prototype --- past future tense
Was, were + predicative (noun, adjective, prepositional phrase...) --- general past tense