[tribby]

a variable font is a more generic term than a metafont. it’s a bit pedantic but while both have parameters, a metafont is usually parametrically generated based on its concept of a pen, whereas a variable font usually has different parameters that have been defined by manual bezier drawings. I don’t remember if metafont itself can produce a variable font but people have used metapost to go to SVG and then UFO (font source) from there

[kragen]

in metafont (the software) you can define a metafont (a font-valued function) in terms of bézier outlines as well as paths stroked with pens; the relevant metafont commands are 'fill' in the first case and 'draw' (rather than postscript's 'stroke') in the second. it doesn't have an equivalent of postscript's 'eofill'. chapter 13 of the metafontbook describes these commands

i don't know if there's a reasonable way to export any standard vector format from metafont; i think there originally wasn't