In English (both UK and US), "metronome" and "metrology" are pronounced as in that spelling, with "tro" instead of "ter".
("Meteorology" is from a different Greek root.)
The important pronunciation difference is whether the Greek root is at the beginning or end of the word.
Unfortunately, Americans often insist on spelling "theater" (as it is pronounced) as "theatre" (to feign Frenchness).
However, "theatrical" is always spelled in an analogous fashion to "metronome", again following pronunciation, where the Greek root is at the beginning.
Note that in both the UK and US, "metre/meter", "litre/liter", "theatre/theater", etc. are always pronounced with "ter".
Also, "meter" meaning measurement device and "parameter" are always spelled "ter" in English.
Since the metric system was first developed in France, French names (metre, litre, etc.) were applied to the new units, but when English-speaking people adopted them, the pronunciations quickly went to "ter".