Or a table with two columns, Key and Value. Index by key. Specify keys in code with constants. No need to alter table when adding new metrics.
If there's something wrong with your DBMS where the alter table to add a row is an expensive or dangerous operation, just add a new table for every attribute, having lots of tables in a database is no worse than having lots of variables in a program.
If your DBA gets angry at you for adding new tables all the time, get a new DBA.