Electric field is not a four vector. They are just three vectors which posses components along three spatial dimension. Their transformation to one form is defined by a $3\times 3$ identity matrix(Euclediian metric).$$E^i = \delta^{ia} E_{a} = E_i.$$ They are also components of elctromagnetic field tensor. Here $E^i$ depicts the $i^{th}$ component of electric field vector is same as the $-c F^{0i}$ th term of electromagnetic field tensor.

Electric field is not a four vector. They are just three vectors which posses components along three spatial dimension. Their transformation to one form is defined by a $3\times 3$ identity matrix(Euclidean metric).$$E^i = \delta^{ia} E_{a} = E_i.$$ They are also components of elctromagnetic field tensor. Here $E^i$ depicts the $i^{th}$ component of electric field vector is same as the $-c F^{0i}$ th term of electromagnetic field tensor.