Many people know far more about English grammar than I, so should you detect a failing in this area on my part, please, notify me.
Some verbs (or “doing words”) are readily recognisable, e.g., run, jump, throw…while others are not so easily detectable.
These include: am, is, was, were, has, have, had, did, do, done.
Sometimes these act as auxiliary (or “helping”) verbs which precede other verbs, e.g., I do think; he is arriving; have they paid?
In the above instances ‘do think’, ‘is arriving’, ‘have…paid’ are examples of what some people term “double verbs”.
The double verb ‘is arriving’ consists of the auxiliary verb ‘is’ and the present participle ‘arriving’. Using the past tense ‘is arriving’ would become ‘had arrived’, with ‘had’ being the auxiliary verb and ‘arrived’, the past participle.