Hi,
1. He is a teacher.
2.The apples taste sweet.
3. He weighs 30 kilos.
Are these sentences in active or passive voice?
Example 1 just equates the two 'things'. Swan's Practical English Usage (Section 457.5) mentions a few active verbs that can sometimes be used with a passive kind of meaning. Your examples 2 and 3 seem to be of this type. Another example would be 'Your report reads well'.
Best wishes, Clive