A strange question: is the form 'do is' correct? For example:
No. do + be by itself is not a valid construction.
One of many possible replacements for your incorrect construction is:
There is a whole class of words used to intensify verbs, adjectives or adverbs in some way. These are the intensifiers. Explaining all of them takes up more room than can reasonably fit in an answer. Just look up each intensifier in a dictionary.
"do" can be used to intensify almost any English verb, in which case it is often written in italics and spoken with heavy emphasis:
Despite the tedious grammar, I do appreciate English.
However, "do" cannot precede an auxiliary verb, where auxiliary verbs include be, will, can, may, etc. The same kind of intensification can still be done, but only by intensifying the auxiliary verb itself:
(EDIT: On a side note, even if 'do' were acceptable, the standard conjugation would be
does be and not
"do is" is wrong here. In this case it would have to be "does be" but while being formed according to the rules of the trade, it would still end up being wrong.
Interesting enough, you can use this combination for the imperative mode: "do be a nice guy and fetch me a beer" is actually fine unless you are a teetotaler.
I don't really know whether there is an actual rule at play here or whether it just managed escaping into the vernacular because of sounding least contorted among its equally logical but impermissible cousins.